Question

dada a pa , determine sua soma ( 2,7,12...4222)

Answer 1

a1 = 2
a2 = 7
r = 7 - 2 = 5 ****
an = 4222
4222 = 2 + ( n - 1) 5
422 = 2 + 5n - 5
422 = 5n - 3
422 + 3 = 5n
5n = 425
n = 425/5 = 85 ***

S85 = ( 2 + 4222)* 42.5
S85 = 42224 * 42.5
S85 = 179520 ****