June 2020 p31 q1
1514
Find the set of values of x for which \(2(3^{1-2x}) < 5^x\). Give your answer in a simplified exact form.
Solution
Start with the inequality \(2(3^{1-2x}) < 5^x\).
Take the natural logarithm of both sides: \(\ln(2) + \ln(3^{1-2x}) < x \ln(5)\).
Apply the logarithm power rule: \(\ln(2) + (1-2x)\ln(3) < x \ln(5)\).
Rearrange the inequality: \(\ln(2) + \ln(3) - 2x \ln(3) < x \ln(5)\).
Combine like terms: \(\ln(6) < x(\ln(5) + 2\ln(3))\).
Solve for \(x\): \(x > \frac{\ln(6)}{\ln(5) + 2\ln(3)}\).
Simplify the denominator: \(x > \frac{\ln(6)}{\ln(45)}\).
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