WAEC SSCE - General Mathematics - 2007 (Objective)

Question 1 Report

If $8^{x+1}=\frac{1}{4}$, find x

$-\frac{5}{3}$ Correct answer

-1

$-\frac{1}{3}$

$\frac{1}{3}$

Answer Details

We can solve the given equation by taking logarithms to the base 2 on both sides. This gives: \begin{align*} 8^{x+1} &= \frac{1}{4}\\ \Rightarrow \quad 2^{3(x+1)} &= 2^{-2}\\ \Rightarrow \quad 3(x+1) &= -2\\ \Rightarrow \quad 3x+3 &= -2\\ \Rightarrow \quad 3x &= -5\\ \Rightarrow \quad x &= -\frac{5}{3} \end{align*} Therefore, the value of $x$ is $-\frac{5}{3}$. So, the correct option is $-\frac{5}{3}$.

Read lesson note on Number Bases (WAEC)

Read lesson note on Modular Arithmetic (WAEC)






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