\(\begin{aligned} & P(n)\\ \implies\, & T(n)>0\\ \implies\, & \frac{n^{2}}{4}+n-13>0\\ \implies\, & \frac{n^{2}+2n+1}{4}+n+1-13>0\\ \implies\, & \frac{\left(n+1\right)^{2}}{4}+\left(n+1\right)-13>0\\ \implies\, & T(n+1)>0\\ \implies\, & P(n+1) \end{aligned}\)