Polynomials: 3 marks Questions (CBSE Class 10)
49 different 3 marks questions on Polynomials from CBSE Class 10 Maths board exams 2022–2026, newest first.
If α , β are zeroes of the polynomial p ( x ) = 5 x 2 − 7 x − 3 , then form a quadratic polynomial whose zeroes are α 2 and β 2 .
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Answer: 3 x 2 + 14 x − 20 (or any non-zero multiple of it)
α + β = 5 7 , α β = − 5 3 Sum = α 2 + β 2 = α β 2 ( α + β ) = − 3/5 14/5 = − 3 14 Product = α β 4 = − 3/5 4 = − 3 20 Polynomial: k ( x 2 + 3 14 x − 3 20 ) ; taking k = 3 , 3 x 2 + 14 x − 20
Find the zeroes of the polynomial p ( x ) = 3 x 2 + 7 x − 20 and verify the relationship between its zeroes and the coefficients.
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Answer: Zeroes: 3 5 and − 4 ; relationship verified.
3 x 2 + 7 x − 20 = 3 x 2 + 12 x − 5 x − 20 = ( 3 x − 5 ) ( x + 4 ) Zeroes: x = 3 5 and x = − 4 Sum = 3 5 − 4 = − 3 7 = − a b Product = 3 5 × ( − 4 ) = − 3 20 = a c . Verified.
Find the zeroes of the polynomial p ( x ) = 4 x 2 − 8 x + 3 and verify the relationship between its zeroes and co-efficients.
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Answer: Zeroes: 2 1 and 2 3 ; relationship verified.
4 x 2 − 8 x + 3 = 4 x 2 − 2 x − 6 x + 3 = ( 2 x − 1 ) ( 2 x − 3 ) Zeroes: 2 1 and 2 3 Sum = 2 1 + 2 3 = 2 = 4 8 = − a b Product = 4 3 = a c . Verified.
Form a polynomial whose zeroes are α 2 and β 2 , where α and β are zeroes of the polynomial p ( x ) = x 2 − 3 2 x + 4 .
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Answer: x 2 − 10 x + 16 (or any non-zero multiple of it)
α + β = 3 2 , α β = 4 α 2 + β 2 = ( α + β ) 2 − 2 α β = 18 − 8 = 10 α 2 β 2 = ( α β ) 2 = 16 Required polynomial: x 2 − 10 x + 16
Find a quadratic polynomial whose sum and product of zeroes are 0 and − 9 , respectively. Also, find the zeroes of the polynomial so obtained.
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Answer: x 2 − 9 ; zeroes 3 and − 3
A quadratic polynomial is x 2 − ( sum ) x + product . p ( x ) = x 2 − 0 ⋅ x + ( − 9 ) = x 2 − 9 .x 2 − 9 = ( x − 3 ) ( x + 3 ) = 0 gives zeroes 3 and − 3 .Check: sum = 0 , product = − 9 .
Find a quadratic polynomial, sum and product of whose zeroes are 5 and − 6 , respectively. Also, find the zeroes of the polynomial so obtained.
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Answer: x 2 − 5 x − 6 ; zeroes 6 and − 1
A quadratic polynomial is x 2 − ( sum ) x + product . p ( x ) = x 2 − 5 x − 6 .x 2 − 5 x − 6 = ( x − 6 ) ( x + 1 ) , so the zeroes are 6 and − 1 .Check: 6 + ( − 1 ) = 5 , 6 × ( − 1 ) = − 6 .
Determine a quadratic polynomial, sum and product of whose zeroes are − 10 and 24, respectively. Also, determine the zeroes of the polynomial so obtained.
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Answer: x 2 + 10 x + 24 ; zeroes − 4 and − 6
A quadratic polynomial is x 2 − ( sum ) x + product . p ( x ) = x 2 − ( − 10 ) x + 24 = x 2 + 10 x + 24 .x 2 + 10 x + 24 = ( x + 4 ) ( x + 6 ) , so the zeroes are − 4 and − 6 .Check: − 4 + ( − 6 ) = − 10 , ( − 4 ) ( − 6 ) = 24 .
Find the zeroes of the polynomial p ( x ) = 3 x 2 − 2 x − 1 and verify the relationship between the zeroes of p(x) and the coefficients of p(x).
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Answer: Zeroes: 1 and − 3 1
3 x 2 − 2 x − 1 = 3 x 2 − 3 x + x − 1 = 3 x ( x − 1 ) + 1 ( x − 1 ) = ( 3 x + 1 ) ( x − 1 ) .Zeroes: x = 1 and x = − 3 1 . Sum = 1 − 3 1 = 3 2 and − a b = − 3 − 2 = 3 2 . Verified. Product = 1 × ( − 3 1 ) = − 3 1 and a c = − 3 1 . Verified.
Find the zeroes of the polynomial p ( x ) = 2 x 2 + 5 x + 2 and verify the relationship between zeroes of p(x) and its coefficients.
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Answer: Zeroes: − 2 1 and − 2
2 x 2 + 5 x + 2 = 2 x 2 + 4 x + x + 2 = 2 x ( x + 2 ) + 1 ( x + 2 ) = ( 2 x + 1 ) ( x + 2 ) .Zeroes: x = − 2 1 and x = − 2 . Sum = − 2 1 − 2 = − 2 5 and − a b = − 2 5 . Verified. Product = ( − 2 1 ) ( − 2 ) = 1 and a c = 2 2 = 1 . Verified.
Find the zeroes of the polynomial q ( x ) = 6 x 2 − 5 x − 1 and verify the relationship between the zeroes of q(x) and its coefficients.
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Answer: Zeroes: 1 and − 6 1
6 x 2 − 5 x − 1 = 6 x 2 − 6 x + x − 1 = 6 x ( x − 1 ) + 1 ( x − 1 ) = ( 6 x + 1 ) ( x − 1 ) .Zeroes: x = 1 and x = − 6 1 . Sum = 1 − 6 1 = 6 5 and − a b = − 6 − 5 = 6 5 . Verified. Product = − 6 1 and a c = − 6 1 . Verified.
Find the zeroes of the polynomial 9 s 2 − 6 s + 1 and verify the relationship between the zeroes and the coefficients of the given polynomial.
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Answer: Zeroes: 3 1 , 3 1
9 s 2 − 6 s + 1 = ( 3 s − 1 ) 2 , so the zeroes are 3 1 and 3 1 .Sum of zeroes = 3 2 and − a b = − 9 − 6 = 3 2 . Verified. Product of zeroes = 9 1 and a c = 9 1 . Verified.
Find the zeroes of the polynomial 4 x 2 + 4 x + 1 and verify the relationship between the zeroes and the coefficients of the given polynomial.
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Answer: Zeroes: − 2 1 , − 2 1
4 x 2 + 4 x + 1 = ( 2 x + 1 ) 2 , so the zeroes are − 2 1 and − 2 1 .Sum of zeroes = − 1 and − a b = − 4 4 = − 1 . Verified. Product of zeroes = 4 1 and a c = 4 1 . Verified.
Find the zeroes of the polynomial 25 a 2 − 10 a + 1 and verify the relationship between the zeroes and coefficients of the given polynomial.
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Answer: Zeroes: 5 1 , 5 1
25 a 2 − 10 a + 1 = ( 5 a − 1 ) 2 , so the zeroes are 5 1 and 5 1 .Sum of zeroes = 5 2 and − a b = − 25 − 10 = 5 2 . Verified. Product of zeroes = 25 1 and a c = 25 1 . Verified.
Find the zeroes of the polynomial p ( x ) = 6 x 2 + 13 x − 5 and verify the relationship between its zeroes and the coefficients.
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Answer: Zeroes 3 1 and − 2 5 ; relationship verified.
6 x 2 + 13 x − 5 = 6 x 2 + 15 x − 2 x − 5 = 3 x ( 2 x + 5 ) − ( 2 x + 5 ) = ( 3 x − 1 ) ( 2 x + 5 ) .Zeroes: x = 3 1 and x = − 2 5 . Sum = 3 1 − 2 5 = − 6 13 and − a b = − 6 13 . Verified. Product = 3 1 × ( − 2 5 ) = − 6 5 and a c = − 6 5 . Verified.
Find the zeroes of the polynomial p ( x ) = 4 x 2 − 4 x − 3 and verify the relationship between zeroes and its coefficients.
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Answer: Zeroes 2 3 and − 2 1 ; relationship verified.
4 x 2 − 4 x − 3 = 4 x 2 − 6 x + 2 x − 3 = 2 x ( 2 x − 3 ) + ( 2 x − 3 ) = ( 2 x + 1 ) ( 2 x − 3 ) .Zeroes: x = 2 3 and x = − 2 1 . Sum = 2 3 − 2 1 = 1 and − a b = 4 4 = 1 . Verified. Product = 2 3 × ( − 2 1 ) = − 4 3 and a c = − 4 3 . Verified.
Find the zeroes of the polynomial p ( x ) = 9 x 2 − 6 x − 35 and verify the relationship between zeroes and its coefficients.
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Answer: Zeroes 3 7 and − 3 5 ; relationship verified.
9 x 2 − 6 x − 35 = 9 x 2 − 21 x + 15 x − 35 = 3 x ( 3 x − 7 ) + 5 ( 3 x − 7 ) = ( 3 x + 5 ) ( 3 x − 7 ) .Zeroes: x = 3 7 and x = − 3 5 . Sum = 3 7 − 3 5 = 3 2 and − a b = 9 6 = 3 2 . Verified. Product = 3 7 × ( − 3 5 ) = − 9 35 and a c = − 9 35 . Verified.
If α , β are zeroes of the polynomial 3 x 2 − 8 x + 4 , then form a quadratic polynomial in x whose zeroes are α 1 and β 1 .
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Answer: x 2 − 2 x + 4 3 , or k ( 4 x 2 − 8 x + 3 )
α + β = 3 8 , α β = 3 4 .Sum of new zeroes = α 1 + β 1 = α β α + β = 4/3 8/3 = 2 . Product of new zeroes = α β 1 = 4 3 . Required polynomial = x 2 − 2 x + 4 3 , or 4 x 2 − 8 x + 3 (any non-zero multiple).
Find zeroes of the polynomial 6 x 2 − 7 x − 3 and verify the relationship between zeroes and its coefficients.
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Answer: Zeroes 2 3 and − 3 1 ; relationship verified.
6 x 2 − 7 x − 3 = 6 x 2 − 9 x + 2 x − 3 = 3 x ( 2 x − 3 ) + 1 ( 2 x − 3 ) = ( 2 x − 3 ) ( 3 x + 1 ) .Zeroes: x = 2 3 and x = − 3 1 . Sum = 2 3 − 3 1 = 6 7 and − a b = − 6 − 7 = 6 7 . Product = 2 3 × ( − 3 1 ) = − 2 1 and a c = 6 − 3 = − 2 1 . Both relations hold.
If α , β are zeroes of the polynomial 8 x 2 − 5 x − 1 , then form a quadratic polynomial in x whose zeroes are α 2 and β 2 .
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Answer: x 2 + 10 x − 32 (or any non-zero multiple k ( x 2 + 10 x − 32 ) )
α + β = 8 5 , α β = − 8 1 .Sum of new zeroes = α 2 + β 2 = α β 2 ( α + β ) = − 8 1 2 × 8 5 = − 10 . Product of new zeroes = α β 4 = − 8 1 4 = − 32 . Required polynomial = x 2 − ( sum ) x + product = x 2 + 10 x − 32 .
Find the zeroes of the polynomial p ( x ) = 3 x 2 + x − 10 and verify the relationship between zeroes and its coefficients.
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Answer: Zeroes: 3 5 and − 2 ; relationship verified.
3 x 2 + x − 10 = 3 x 2 + 6 x − 5 x − 10 = 3 x ( x + 2 ) − 5 ( x + 2 ) = ( 3 x − 5 ) ( x + 2 ) .Zeroes: x = 3 5 , x = − 2 . Sum = 3 5 − 2 = − 3 1 and − a b = − 3 1 . Product = 3 5 × ( − 2 ) = − 3 10 and a c = − 3 10 . Hence the relationship is verified.
α , β are zeroes of the polynomial 3 x 2 − 8 x + k . Find the value of k, if α 2 + β 2 = 9 40 .
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Answer: k = 4
α + β = 3 8 , α β = 3 k .α 2 + β 2 = ( α + β ) 2 − 2 α β = 9 64 − 3 2 k .9 64 − 3 2 k = 9 40 , so 3 2 k = 9 24 = 3 8 and k = 4 .
Find the zeroes of the polynomial 2 x 2 + 7 x + 5 and verify the relationship between its zeroes and co-efficients.
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Answer: Zeroes: − 1 and − 2 5 ; relationship verified.
2 x 2 + 7 x + 5 = 2 x 2 + 2 x + 5 x + 5 = 2 x ( x + 1 ) + 5 ( x + 1 ) = ( 2 x + 5 ) ( x + 1 ) .Zeroes: x = − 1 , x = − 2 5 . Sum = − 1 − 2 5 = − 2 7 and − a b = − 2 7 . Product = ( − 1 ) ( − 2 5 ) = 2 5 and a c = 2 5 . Hence verified.
α and β are zeroes of a quadratic polynomial p x 2 + q x + 1 . Form a quadratic polynomial whose zeroes are α 2 and β 2 .
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Answer: x 2 + 2 q x + 4 p (or any non-zero multiple k ( x 2 + 2 q x + 4 p ) )
α + β = − p q , α β = p 1 Sum of new zeroes = α 2 + β 2 = α β 2 ( α + β ) = 1/ p 2 ( − q / p ) = − 2 q Product = α β 4 = 4 p Required polynomial = x 2 − ( − 2 q ) x + 4 p = x 2 + 2 q x + 4 p
α and β are zeroes of a quadratic polynomial x 2 − a x − b . Obtain a quadratic polynomial whose zeroes are 3 α + 1 and 3 β + 1 .
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Answer: x 2 − ( 3 a + 2 ) x + ( 3 a − 9 b + 1 ) (or any non-zero multiple)
α + β = a , α β = − b Sum of new zeroes = 3 ( α + β ) + 2 = 3 a + 2 Product = 9 α β + 3 ( α + β ) + 1 = − 9 b + 3 a + 1 Required polynomial = x 2 − ( 3 a + 2 ) x + ( 3 a − 9 b + 1 )
If α and β are the zeroes of the polynomial a x 2 − x + c . Obtain a polynomial whose zeroes are α − 3 and β − 3 .
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Answer: a x 2 + ( 6 a − 1 ) x + ( 9 a + c − 3 ) (or any non-zero multiple)
α + β = a 1 , α β = a c Sum of new zeroes = ( α + β ) − 6 = a 1 − 6 a Product = α β − 3 ( α + β ) + 9 = a c − 3 + 9 a Polynomial = x 2 − a 1 − 6 a x + a 9 a + c − 3 Multiplying by a : a x 2 + ( 6 a − 1 ) x + ( 9 a + c − 3 )
Obtain the zeroes of the polynomial 7 x 2 + 18 x − 9 . Hence, write a polynomial each of whose zeroes is twice the zeroes of given polynomial.
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Answer: Zeroes: 7 3 and − 3 ; required polynomial: k ( 7 x 2 + 36 x − 36 ) , e.g. 7 x 2 + 36 x − 36
7 x 2 + 18 x − 9 = 7 x 2 + 21 x − 3 x − 9 = ( 7 x − 3 ) ( x + 3 ) Zeroes: 7 3 and − 3 New zeroes: 7 6 and − 6 Sum = 7 6 − 6 = − 7 36 , product = − 7 36 Polynomial: x 2 + 7 36 x − 7 36 , i.e. k ( 7 x 2 + 36 x − 36 )
Obtain the zeroes of the polynomial p ( x ) = 2 x 2 − 5 x − 3 . Hence, obtain a polynomial each of whose zeroes is one less than each of the zero of p ( x ) .
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Answer: Zeroes: 3 and − 2 1 ; required polynomial: k ( 2 x 2 − x − 6 ) , e.g. 2 x 2 − x − 6
2 x 2 − 5 x − 3 = 2 x 2 − 6 x + x − 3 = ( 2 x + 1 ) ( x − 3 ) Zeroes: 3 and − 2 1 New zeroes: 2 and − 2 3 Sum = 2 1 , product = − 3 Polynomial: x 2 − 2 1 x − 3 , i.e. k ( 2 x 2 − x − 6 )
Find the zeroes of the polynomial p ( x ) = 6 x 2 − 5 x − 1 . Hence, obtain a polynomial each of whose zeroes is three times the zeroes of p ( x ) .
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Answer: Zeroes: 1 and − 6 1 ; required polynomial: k ( 2 x 2 − 5 x − 3 ) , e.g. 2 x 2 − 5 x − 3
6 x 2 − 5 x − 1 = 6 x 2 − 6 x + x − 1 = ( 6 x + 1 ) ( x − 1 ) Zeroes: 1 and − 6 1 New zeroes: 3 and − 2 1 Sum = 2 5 , product = − 2 3 Polynomial: x 2 − 2 5 x − 2 3 , i.e. k ( 2 x 2 − 5 x − 3 )
Find the zeroes of the polynomial p ( x ) = 3 x 2 − 4 x − 4 . Hence, write a polynomial whose each of the zeroes is 2 more than zeroes of p ( x ) .
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Answer: Zeroes: 2 and − 3 2 ; required polynomial: 3 x 2 − 16 x + 16 (or any non-zero multiple)
3 x 2 − 4 x − 4 = 3 x 2 − 6 x + 2 x − 4 = ( 3 x + 2 ) ( x − 2 ) Zeroes: x = 2 and x = − 3 2 New zeroes: 4 and 3 4 Sum = 3 16 , product = 3 16 Polynomial: k ( x 2 − 3 16 x + 3 16 ) ; with k = 3 : 3 x 2 − 16 x + 16
Find the zeroes of the polynomial q ( x ) = 8 x 2 − 2 x − 3 . Hence, find a polynomial whose zeroes are 2 less than the zeroes of q ( x ) .
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Answer: Zeroes: 4 3 and − 2 1 ; required polynomial: 8 x 2 + 30 x + 25 (or any non-zero multiple)
8 x 2 − 2 x − 3 = 8 x 2 − 6 x + 4 x − 3 = ( 4 x − 3 ) ( 2 x + 1 ) Zeroes: x = 4 3 and x = − 2 1 New zeroes: 4 3 − 2 = − 4 5 and − 2 1 − 2 = − 2 5 Sum = − 4 15 , product = 8 25 Polynomial: k ( x 2 + 4 15 x + 8 25 ) ; with k = 8 : 8 x 2 + 30 x + 25
Find the zeroes of the polynomial r ( x ) = 4 x 2 + 3 x − 1 . Hence, write a polynomial whose zeroes are reciprocal of the zeroes of polynomial r ( x ) .
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Answer: Zeroes: 4 1 and − 1 ; required polynomial: x 2 − 3 x − 4 (or any non-zero multiple)
4 x 2 + 3 x − 1 = 4 x 2 + 4 x − x − 1 = ( 4 x − 1 ) ( x + 1 ) Zeroes: x = 4 1 and x = − 1 Reciprocals: 4 and − 1 Sum = 3 , product = − 4 Polynomial: x 2 − 3 x − 4
Zeroes of the quadratic polynomial x 2 − 3 x + 2 are α and β . Construct a quadratic polynomial whose zeroes are 2 α + 1 and 2 β + 1 .
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Answer: x 2 − 8 x + 15 (or any non-zero multiple)
α + β = 3 and α β = 2 Sum of new zeroes = 2 ( α + β ) + 2 = 6 + 2 = 8 Product = 4 α β + 2 ( α + β ) + 1 = 8 + 6 + 1 = 15 Required polynomial = x 2 − 8 x + 15 (or k ( x 2 − 8 x + 15 ) , k = 0 )
Find the zeroes of the polynomial 4 x 2 − 4 x + 1 and verify the relationship between the zeroes and the coefficients.
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Answer: Zeroes: 2 1 , 2 1 ; relationship verified.
4 x 2 − 4 x + 1 = ( 2 x − 1 ) 2 , so the zeroes are 2 1 and 2 1 .Sum of zeroes = 1 and − a b = − 4 − 4 = 1 . Product of zeroes = 4 1 and a c = 4 1 . Both relations hold.
Zeroes of the quadratic polynomial x 2 + x − 6 are ‘α ’ and ‘β ’. Construct a quadratic polynomial whose zeroes are α 1 and β 1 .
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Answer: 6 x 2 − x − 1 (or any non-zero multiple)
α + β = − 1 and α β = − 6 Sum of new zeroes = α 1 + β 1 = α β α + β = − 6 − 1 = 6 1 Product = α β 1 = − 6 1 Polynomial = x 2 − 6 1 x − 6 1 , i.e. 6 x 2 − x − 1 (or k ( 6 x 2 − x − 1 ) , k = 0 )
Find the zeroes of the polynomial 2 x 2 + 3 x − 2 and verify the relationship between the zeroes and the coefficients.
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Answer: Zeroes: 2 1 , − 2 ; relationship verified.
2 x 2 + 3 x − 2 = 2 x 2 + 4 x − x − 2 = ( 2 x − 1 ) ( x + 2 ) , so zeroes are 2 1 and − 2 .Sum = 2 1 − 2 = − 2 3 and − a b = − 2 3 . Product = 2 1 × ( − 2 ) = − 1 and a c = 2 − 2 = − 1 . Both relations hold.
Find the zeroes of the quadratic polynomial 5 x 2 + 3 x − 2 and verify the relationship between the zeroes and the co-efficients.
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Answer: Zeroes are 5 2 and − 1 ; relationship verified.
5 x 2 + 3 x − 2 = 5 x 2 + 5 x − 2 x − 2 = ( 5 x − 2 ) ( x + 1 ) .Zeroes: x = 5 2 and x = − 1 . Sum = 5 2 − 1 = − 5 3 = − a b . Product = 5 2 × ( − 1 ) = − 5 2 = a c . Hence the relationship is verified.
Find the zeroes of the polynomial 2 x 2 + 3 x − 9 and verify the relationship between the zeroes and the co-efficients of polynomial.
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Answer: Zeroes are 2 3 and − 3 ; relationship verified.
2 x 2 + 3 x − 9 = 2 x 2 + 6 x − 3 x − 9 = ( 2 x − 3 ) ( x + 3 ) .Zeroes: x = 2 3 and x = − 3 . Sum = 2 3 − 3 = − 2 3 = − a b . Product = 2 3 × ( − 3 ) = − 2 9 = a c . Hence the relationship is verified.
If one zero of the polynomial x 2 − 8 x + k exceeds the other by 2, then find the zeroes and the value of k.
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Answer: Zeroes are 3 and 5; k = 15
Let the zeroes be α and α + 2 . Sum of zeroes = 2 α + 2 = 8 , so α = 3 ; the zeroes are 3 and 5. Product of zeroes = k = 3 × 5 = 15 .
Find the zeroes of the quadratic polynomial 6 x 2 − 7 x − 3 and verify the relationship between the zeroes and the coefficients of the polynomial.
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Answer: Zeroes are 2 3 and − 3 1 ; relationship verified.
6 x 2 − 7 x − 3 = 6 x 2 − 9 x + 2 x − 3 = 3 x ( 2 x − 3 ) + 1 ( 2 x − 3 ) = ( 2 x − 3 ) ( 3 x + 1 ) .Zeroes: x = 2 3 and x = − 3 1 . Sum = 2 3 − 3 1 = 6 7 and − a b = − 6 − 7 = 6 7 . Product = 2 3 × ( − 3 1 ) = − 2 1 and a c = 6 − 3 = − 2 1 . Hence the relationship is verified.
Find the zeroes of the polynomial 3 x 2 − 5 x − 2 and verify the relationship between the zeroes and the coefficients of the polynomial.
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Answer: Zeroes are 2 and − 3 1 ; relationship verified.
3 x 2 − 5 x − 2 = 3 x 2 − 6 x + x − 2 = 3 x ( x − 2 ) + 1 ( x − 2 ) = ( x − 2 ) ( 3 x + 1 ) .Zeroes: x = 2 and x = − 3 1 . Sum = 2 − 3 1 = 3 5 and − a b = − 3 − 5 = 3 5 . Product = 2 × ( − 3 1 ) = − 3 2 and a c = 3 − 2 . Hence the relationship is verified.
Find the zeroes of the quadratic polynomial x 2 − 15 and verify the relationship between the zeroes and the coefficients of the polynomial.
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Answer: Zeroes:
15 and
− 15 ; relationship verified.
x 2 − 15 = ( x − 15 ) ( x + 15 ) , so the zeroes are 15 and − 15 .Here a = 1 , b = 0 , c = − 15 . Sum of zeroes = 15 + ( − 15 ) = 0 = a − b = 1 − 0 . Product of zeroes = 15 × ( − 15 ) = − 15 = a c = 1 − 15 . Hence the relationship is verified.
Find the zeroes of the polynomial 4 x 2 + 4 x − 3 and verify the relationship between zeroes and coefficients of the polynomial.
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Answer: Zeroes are 2 1 and − 2 3 ; relationship verified.
4 x 2 + 4 x − 3 = 4 x 2 + 6 x − 2 x − 3 = 2 x ( 2 x + 3 ) − 1 ( 2 x + 3 ) = ( 2 x − 1 ) ( 2 x + 3 ) .Zeroes: x = 2 1 and x = − 2 3 . Sum = 2 1 − 2 3 = − 1 and − a b = − 4 4 = − 1 . Product = 2 1 × ( − 2 3 ) = − 4 3 and a c = − 4 3 . Hence the relationship is verified.
If α and β are the zeroes of the polynomial x 2 + x − 2 , then find the value of β α + α β .
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Answer: − 2 5
α + β = − 1 and α β = − 2 .α 2 + β 2 = ( α + β ) 2 − 2 α β = 1 + 4 = 5 .β α + α β = α β α 2 + β 2 = − 2 5 = − 2 5 .
If α , β are zeroes of the quadratic polynomial x 2 + 3 x + 2 , find a quadratic polynomial whose zeroes are α + 1 , β + 1 .
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Answer: x 2 + x
α + β = − 3 , α β = 2 Sum of new zeroes = ( α + 1 ) + ( β + 1 ) = − 3 + 2 = − 1 Product = ( α + 1 ) ( β + 1 ) = α β + ( α + β ) + 1 = 2 − 3 + 1 = 0 Required polynomial = x 2 − ( sum ) x + product = x 2 + x
Find the zeroes of the polynomial p ( x ) = 2 x 2 − 7 x − 15 and verify the relationship between its coefficients and zeroes.
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Answer: Zeroes: 5 and − 2 3
2 x 2 − 7 x − 15 = 2 x 2 − 10 x + 3 x − 15 = ( x − 5 ) ( 2 x + 3 ) Zeroes: x = 5 and x = − 2 3 Sum = 5 − 2 3 = 2 7 and − a b = − 2 − 7 = 2 7 ✓ Product = 5 × ( − 2 3 ) = − 2 15 and a c = − 2 15 ✓
Find the zeroes of the polynomial p ( x ) = 3 x 2 + 5 x − 28 and verify the relationship between its coefficients and zeroes.
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Answer: Zeroes: 3 7 and − 4
3 x 2 + 5 x − 28 = 3 x 2 + 12 x − 7 x − 28 = ( x + 4 ) ( 3 x − 7 ) Zeroes: x = − 4 and x = 3 7 Sum = 3 7 − 4 = − 3 5 and − a b = − 3 5 ✓ Product = 3 7 × ( − 4 ) = − 3 28 and a c = − 3 28 ✓
Find the zeroes of the quadratic polynomial x 2 + 6 x + 8 and verify the relationship between the zeroes and the coefficients.
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Answer: Zeroes: − 2 and − 4 (sum = − 6 = − a b , product = 8 = a c ).
x 2 + 6 x + 8 = x 2 + 2 x + 4 x + 8 = ( x + 2 ) ( x + 4 ) .Zeroes are − 2 and − 4 . Sum of zeroes = − 6 and − a b = − 1 6 = − 6 . Verified. Product of zeroes = 8 and a c = 1 8 = 8 . Verified.
If α , β are zeroes of the quadratic polynomial x 2 − 5 x + 6 , form another quadratic polynomial whose zeroes are α 1 , β 1 .
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Answer: x 2 − 6 5 x + 6 1 , or k ( 6 x 2 − 5 x + 1 ) for any non-zero k
α + β = 5 , α β = 6 .Sum of new zeroes = α 1 + β 1 = α β α + β = 6 5 . Product of new zeroes = α β 1 = 6 1 . Required polynomial = x 2 − 6 5 x + 6 1 , i.e. 6 1 ( 6 x 2 − 5 x + 1 ) ; so 6 x 2 − 5 x + 1 (or any non-zero multiple).
If α and β are roots of the quadratic equation x 2 − 7 x + 10 = 0 , find the quadratic equation whose roots are α 2 and β 2 .
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Answer: x 2 − 29 x + 100 = 0
α + β = 7 , α β = 10 .α 2 + β 2 = ( α + β ) 2 − 2 α β = 49 − 20 = 29 α 2 β 2 = 100 Required equation: x 2 − 29 x + 100 = 0
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