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If $9^x + 3^x = 240$, determine the value of $3^x$ and then, by using logarithms, find $x$ correct to $4$ significant figures.
Mathematics 9709 · AS & A Level · Logarithmic and exponential functions
Logarithmic and exponential functions — practice question
Worked solution & mark scheme
This 5-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Notice that $9^x$ may be rewritten as $(3^x)^2$ or as $3^{2x}$” …
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