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WAEC Further Mathematics 2014 Paper

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Question : 1

Total: 40

If

\;\frac{1}{5^{-y}} = 25(5^{4-2y})

, find the value of y.

4
2
-4
-5

Solution:

$\;\frac{1}{5^{-y}} = 25(5^{4-2y})$

$\implies 5^{y} = (5^{2})(5^{4-2y})$

$5^{y} = 5^{2+4-2y}$

Comparing bases, we have

$y = 6 - 2y$

$3y = 6 \implies y = 2$

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