Past papers › WAEC · 2023 · May/June · General Maths · Paper 1 › Question 50 Question WAEC General Maths 2023 Objective Expressions, formulae & change of subject Quadratics & their graphs Expressions, formulae & change of subject, Quadratics & their graphs
WAEC 2023 · Paper 1 · Q50 For what values of x x x x 2 + 2 10 x 2 − 13 x − 3 \dfrac{x^2 + 2}{10x^2 - 13x - 3} 10 x 2 − 13 x − 3 x 2 + 2
A 3 2 , 1 5 \frac32, \frac15 2 3 , 5 1 B − 3 2 , − 1 5 -\frac32, -\frac15 − 2 3 , − 5 1 C 3 2 , − 1 5 \frac32, -\frac15 2 3 , − 5 1 D − 3 2 , 1 5 -\frac32, \frac15 − 2 3 , 5 1
Worked solution (try it first) The fraction is undefined when the bottom is zero:
10 x 2 − 13 x − 3 = 0 10x^2 - 13x - 3 = 0 10 x 2 − 13 x − 3 = 0 .
Factorise (numbers
− 15 -15 − 15 and
2 2 2 multiply to
− 30 -30 − 30 and add to
− 13 -13 − 13 ):
( 5 x + 1 ) ( 2 x − 3 ) = 0 (5x + 1)(2x - 3) = 0 ( 5 x + 1 ) ( 2 x − 3 ) = 0 .
So
x = − 1 5 x = -\frac15 x = − 5 1 or
x = 3 2 x = \frac32 x = 2 3 , option C.
Watch out
5 x + 1 = 0 5x + 1 = 0 5 x + 1 = 0 x = − 1 5 x = -\frac15 x = − 5 1 2 x − 3 = 0 2x - 3 = 0 2 x − 3 = 0 x = 3 2 x = \frac32 x = 2 3 1 5 \frac15 5 1 − 3 2 -\frac32 − 2 3 Report a problem with this question