Question

calcule a soma dos 7 primeiros termos da PG ( 1/8 , -1/4 , 1/2 ...) calcule por favor

Answer 1

a1 = 1/8
a2 = -1/4
q = -1/4 :  1/8 =  - 1/4 * 8/1= - 8/4 = - 2 ***
n = 7

S7 =  1/8 . ( -2⁷  - 1)/ (7-1)
S7 = 1/8 ( -128 - 1)/6
S7 = 1/8 ( - 129 )/6
S7 = [1/8  * ( - 129) ] /6
S7 = ( - 129/8 ) /6
S7 = ( -129/8 : 6/1 =  - 129/8 *  1/6 = -  129/48 ****