Answer
$\log_5 \dfrac{x^4}{x+1}$
Work Step by Step
Using the properties of logarithms, then,
\begin{array}{l}
\log_5 x+3\log_5 x-\log_5 (x+1)
\\\\=
\log_5 x+\log_5 x^3-\log_5 (x+1)
\\\\=
\log_5 \dfrac{x\cdot x^3}{x+1}
\\\\=
\log_5 \dfrac{x^4}{x+1}
.\end{array}
