# How can I evaluate the following $\sum_{0 \le k \le n^2} 7k+6x$

$$\sum_{0 \le k \le n^2} 7k+6x$$

$\sum_{k=0}^{n^2} (7k+6x)=7\sum k+6x\sum 1=\frac{7n^2(n^2+1)}{2}+6x(n^2+1)=\frac{(7n^2+12x)(n^2+1)}{2}$