Find the equation whose roots are \(\frac{2}{3}and \frac{-1}{4}\)

MATHEMATICS
WAEC 1998

Find the equation whose roots are \(\frac{2}{3}and \frac{-1}{4}\)

  • A. \(12x^2-5x-2=0\)
  • B. \(12x^2-11x+2=0\)
  • C. \(x^2-\frac{11}{12}x+2=0\)
  • D. \(x^2+\frac{11}{12}x-2=0\)

Correct Answer: A. \(12x^2-5x-2=0\)

Explanation

x\(^2\) - (sum of given roots)x + (product of given roots ) = 0

x\(^2\) - (\(\frac{2}{3} + \frac{-1}{4}\))x + (\(\frac{2}{3} * \frac{-1}{4}\)) = 0

x\(^2\) - (\(\frac{8 - 3}{12}\))x + (\(\frac{- 2}{12}\))

x\(^2\) - \(\frac{5}{12}\)x + \(\frac{- 2}{12}\)

multiply through by the LCM 12

12 * x\(^2\) - 12 * \(\frac{5}{12}\)x + 12 * \(\frac{- 2}{12}\)

12x\(^2\) - 5x - 2 = 0



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