JAMB Mathematics 2020 Paper

Concept:The expression is simplified by factoring both numerator and denominator, then cancelling the common factor.Explanation:Start with the numerator: $324 - 4x^2$.Factor out the common factor $4$: $4(81 - x^2)$.Recognise $81 - x^2$ as a difference of two squares: $81 - x^2 = (9 - x)(9 + x)$.So the numerator becomes $4(9 - x)(9 + x)$.Now factor the denominator: $2x + 18 = 2(x + 9)$.Rewrite the fraction: $$\frac{4(9 - x)(9 + x)}{2(x + 9)}$$.Cancel the common factor $(9 + x)$: $\frac{4}{2}(9 - x) = 2(9 - x)$.Since $2(9 - x) = 18 - 2x$ and $-2(x - 9) = -2x + 18$, both are equal.Therefore, the simplified form is $-2(x - 9)$.Answer:D. $-2(x - 9)$