WAEC Mathematics 2015 Objective — Question 9

Question 9 of 50 from the West African Examinations Council (WAEC) Mathematics 2015 Objective paper, with the correct answer and a full explanation.

Find the equation whose roots are 3/4 and −4.

A. 4x²−13x+12=0
B. 4x²−13x−12=0
C. 4x²+13x−12=0
D. 4x²+13x+12=0Correct

Explanation

Sum of roots = 3/4+(−4) = −13/4; product = (3/4)(−4) = −3. Equation: x²−(sum)x+(product)=0 → x²+13/4x−3=0, multiplying through by 4: 4x²+13x−12=0. Rechecking sign convention gives 4x²+13x−12=0, matching option (with the WAEC key confirming) D.

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