1² + 2² + 3² + 4²

30

(6(2) − 2²) + (6(3) − 3²) + (6(4) − 4²) + (6(5) − 5²) + (6(6) − 6²)
Now evaluate the sum.

Follow the same process as shown in parts (a) and (b).
Be sure to note the starting and ending indices!