If the sum of the roots of the equation (x - p)(2x - 1) -

MATHEMATICS
WAEC 2010

If the sum of the roots of the equation (x - p)(2x - 1) - 0 is 1, find the value of x

  • A. 1\(\frac{1}{2}\)
  • B. \(\frac{1}{2}\)
  • C. -\(\frac{3}{2}\)
  • D. -1\(\frac{1}{2}\)

Correct Answer: A. 1\(\frac{1}{2}\)

Explanation

(x - p)(2x + 1) = 0

2x2 + x - 2px - p = 0

2x2 + x (1 - 2p) - p = 0

2x2 - (2p - 1)x - p = 0

divide through by 2

x2 - \(\frac{(2p - 1)}{2}\)x - \(\frac{p}{2}\) = 0

compare to x2 - (sum of roots)x + product of roots = 0

sum of roots = \(\frac{2p - 1}{2}\)

But sum of roots = 1

Given; \(\frac{2p - 1}{2}\) = 1

2p - 1 = 2 x 1

2p - 1 = 2

2p = 2 + 1 = 3

p = \(\frac{3}{2}\)

p = 1\(\frac{1}{2}\)



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