WAEC 2020 · Paper 1 · Q21

Expressions, formulae & change of subject

The expression $\dfrac{5x + 3}{6x(x + 1)}$ will be undefined when $x$ equals

Worked solution (try it first)

The expression is undefined when the bottom $6x(x + 1)$ is zero.
$6x = 0$ gives $x = 0$ , and $x + 1 = 0$ gives $x = -1$ .
So $x \in \{0, -1\}$ , option B.

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