WAEC 2019 · Paper 1 · Q22

Indices & standard form

If $2^a = \sqrt{64}$ and $\frac ba = 3$ , evaluate $a^2 + b^2$ .

Worked solution (try it first)

$\sqrt{64} = 8 = 2^3$ , so $2^a = 2^3$ and $a = 3$ .
$\frac ba = 3$ means $b = 3a = 9$ .
So $a^2 + b^2 = 9 + 81 = 90$ , option C.

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