Answer
$\log_{5} (\frac{x^{4}}{x+1})$
Work Step by Step
$\log_{5} x+3\log_{5} x-\log_{5}(x+1)$
=$\log_{5} x+\log_{5} x^{3}-\log_{5}(x+1)$
=$\log_{5} (x\times x^{3})-\log_{5}(x+1)$
=$\log_{5} (x^{4})-\log_{5}(x+1)$
=$\log_{5} (\frac{x^{4}}{x+1})$