Split the summation to make the starting value of equal to .

Split the summation into smaller summations that fit the summation rules.

Evaluate .

The formula for the summation of a polynomial with degree is:

Substitute the values into the formula and make sure to multiply by the front term.

Simplify.

Add and .

Multiply by .

Divide by .

Multiply by .

Evaluate .

The formula for the summation of a constant is:

Substitute the values into the formula.

Simplify.

Remove parentheses.

Multiply by .

Add the results of the summations.

Subtract from .

Expand the series for each value of .

Simplify.

Multiply by .

Subtract from .

Replace the summations with the values found.

Add and .

Evaluate sum from i=2 to 7 of 3i-15