Solve the equation \(\ln(x^3 - 3) = 3 \ln x - \ln 3\). Give your answer correct to 3 significant figures.
Solution
Start with the given equation:
\(\ln(x^3 - 3) = 3 \ln x - \ln 3\)
Apply the logarithm property \(a \ln b = \ln(b^a)\):
\(\ln(x^3 - 3) = \ln(x^3) - \ln 3\)
Use the property \(\ln a - \ln b = \ln\left(\frac{a}{b}\right)\):
\(\ln(x^3 - 3) = \ln\left(\frac{x^3}{3}\right)\)
Since the logarithms are equal, set the arguments equal:
\(x^3 - 3 = \frac{x^3}{3}\)
Multiply through by 3 to clear the fraction:
\(3(x^3 - 3) = x^3\)
\(3x^3 - 9 = x^3\)
Rearrange to solve for \(x^3\):
\(3x^3 - x^3 = 9\)
\(2x^3 = 9\)
Divide by 2:
\(x^3 = \frac{9}{2}\)
Take the cube root:
\(x = \sqrt[3]{\frac{9}{2}}\)
Calculate \(x\) to 3 significant figures:
\(x \approx 1.65\)
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