

InterviewSolution
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Find the zeros of each of the following quadratic polynomials and verify the relationship between the zeros and their coefficients:(i) f(x) = x2 - 2x - 8(ii) g(s) = 4s2 - 4s + 1(iii) h(t) = t2 - 15(iv) 6x2 - 3 - 7x |
Answer» (i) f(x) = x2 - 2x - 8 factorize the given polynomial by splitting the middle term: ⇒ x2 - 4x + 2x – 8 ⇒ x (x - 4) + 2 (x - 4) For zeros of f(x), f(x) = 0 ⇒(x + 2) (x - 4) = 0x+2 = 0x = - 2x - 4 = 0x = 4 ⇒x = - 2, 4 Therefore zeros of the polynomial are - 2 & 4 In a polynomial the relations hold are as follows: sum of zeroes is equal to - \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\) product of zeroes is equal to \(\frac{Constant\,term}{coefficient\,of\,x^2}\) For the given polynomial, Sum of zeros = - 2 + 4 = 2 And - \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\) is - (- 2) = 2 Hence the value of - \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\) and sum of zeroes are same. Product of zeros = - 2 × 4 = - 8 \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\) is - 8. Hence the value of \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\) and product of zeroes are same. (ii) g(s) = 4s2 - 4s + 1 factorize the given polynomial by splitting the middle term: ⇒ 4s2 - 2s - 2s + 1 ⇒ 2s (2s - 1) - 1 (2s - 1) For zeros of g(s), g(s) = 0 (2s - 1) (2s - 1) = 0 2s - 1 = 0 s = \(\frac{1}{2}\) Therefore zeros of the polynomial are \(\frac{1}{2}\), \(\frac{1}{2}\) In a polynomial the relations hold are as follows: sum of zeroes is equal to - \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\) product of zeroes is equal to \(\frac{Constant\,term}{coefficient\,of\,x^2}\) For the given polynomial, Sum of zeros = \(\frac{1}{2}\) + \(\frac{1}{2}\) = 1 \(\frac{-Coefficient\,of\,s}{Coeficient\,of\,s^2}\) = \(\frac{4}{4}\) = 1 Hence the value of - \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\) and sum of zeroes are same. Product of zeros = - \(\frac{1}{2}\) × - \(\frac{1}{2}\) = \(\frac{1}{4}\) \(\frac{Constant\,term}{coefficient\,of\,s^2}\) = \(\frac{1}{4}\) Hence the value of \(\frac{Constant\,term}{coefficient\,of\,x^2}\) and product of zeroes are same. (iii) h(t) = t2 - 15 use the formula a2 - b2 = (a+ b)(a - b) to solve the above equation, Here a is t and b is √15. Solve the given expression as: t2 - (√15)2 = (t + √15)(t - √15) For zeros of h(t), h(t) = 0 t + √15 = 0 t = - √15 t - √15 = 0 t = √15 Therefore zeros of the given polynomial are t = √15 & -√15 In a polynomial the relations hold are as follows: sum of zeroes is equal to - \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\) product of zeroes is equal to \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\) For the given polynomial, Sum of zeros = √15 + (- √15) = 0 The value of - \(\frac{Coefficient\,of\,t}{Coeficient\,of\,t^2}\) is 0. Hence, the value of - \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\)and sum of zeroes are same. Product of zeros = - √15 x √15 The value of \(\frac{Constant\,term}{coefficient\,of\,t^2}\) is - √15 Hence the value of \(\frac{Constant\,term}{coefficient\,of\,x^2}\) and product of zeroes are same. (iv) f(x) = 6x2 - 3 - 7x Write the equation in the form of ax2 +bx+c as: 6x2 - 7x -3 factorize the given polynomial by splitting the middle term: ⇒ 6x2 - 9x + 2x - 3 ⇒ 3x(2x - 3) +1(2x - 3) ⇒ (3x + 1) (2x - 3) For zeros of f(x),f(x) = 0 ⇒ (3x + 1) (2x - 3) = 0 x = \(\frac{-1}{3}\), \(\frac{3}{2}\) Therefore zeros of the polynomial are \(\frac{-1}{3}\), \(\frac{3}{2}\) In a polynomial the relations hold are as follows: sum of zeroes is equal to - \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\) product of zeroes is equal to \(\frac{Constant\,term}{coefficient\,of\,x^2}\) Sum of zeros = \(\frac{-1}{3}\) + \(\frac{3}{2}\) = \(\frac{-2+9}{2}\) = \(\frac{7}{6}\) = \(\frac{7}{6}\) = - \(\frac{Coefficient\,of\,x}{Coeficient\,of\,x^2}\) Product of zeros = \(\frac{-1}{3}\)× \(\frac{3}{2}\) = \(\frac{-3}{6}\) = \(\frac{-1}{2}\) = \(\frac{Constant\,term}{coefficient\,of\,x^2}\) |
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