(a) Find each sum.
1 + 2 + 3 + 4 + 5 = ?
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 = ?
1 + 2 + 3 + 4 + 5 + 6
+ 7 + 8 + 9 + 10 = ?
(b) Use the formula below for the sum of the first n natural numbers to verify your answers to part (a).
1 + 2 + 3 + . . . + n = 1/2n (n + 1)
(c) Use the formula in part (b) to find n such that the sum of the first n natural numbers is 210?