Polynomials · Class 10 · CBSE Mathematics

If the squared difference of the zeroes of the quadratic polynomial f(x) = x^2 + px + 45 is equal to 144, find the value of p.

Practice question from Polynomials (Class 10 · CBSE Mathematics), with the correct answer and a step-by-step solution.

hard · MCQ · Q-DF85C4

If the squared difference of the zeroes of the quadratic polynomial f(x)=x2+px+45f(x) = x^2 + px + 45 is equal to 144, find the value of pp.

  1. A.±12
  2. B.±18Correct answer
  3. C.±6
  4. D.±9

Solution

Let zeroes be α\alpha and eta. We have \alpha + eta = -p and \alphaeta = 45. Given (\alpha - eta)^2 = 144, which expands to (\alpha + eta)^2 - 4\alphaeta = 144. Substituting the values: (−p)2−4(45)=144  ⟹  p2−180=144  ⟹  p2=324(-p)^2 - 4(45) = 144 \implies p^2 - 180 = 144 \implies p^2 = 324, so p=±18p = \pm 18.

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