Question

Apply root test to the series.

Answer 1

$\displaystyle\lim_{n\to\infty}\sqrt[n]{\left|\left(\frac{5n+15}{2n-1}\right)^n\right|}=\lim_{n\to\infty}\frac{5n+15}{2n-1}=\dfrac52$

Since this limit exceeds 1, the series diverges.