Reflection across the y-axis
H(4, -3), (3, 1), J5, -1)

His allows you to set up a summation of the form:

Summation from i = 1 to 500 of i.

The general solution to the summation of i from 1 to n is n(n+1)/2. In this case, n = 500.

500(501)/2 = 125250

Recall that you divided the sum by 2 to simplify its computation. Now multiply your result by 2 for your final

125250 * 2 = 250500