Question

calcule a soma dos 20 primeiros termos da PG,cuja razão e 5 eo primeiro termo hlé igual 1/5.

Answer 1

q⇒ 5

an= a1 *q^n -1
a20= 1/5 * 5^20-1
a20= 1/5 * 5^19
a20= 1/5 * 19.073.486.238.125
a20= 3.814.697.265.625

S20= ((a1 + an) * n)/2
S20 = ((1/5 + 3.814.697.265.625) * 20)/2
S20 = ((1/5 +  19.073.486.238.125/5) * 20)/2
S20= (19.073.486.238.126/5) * 20)/2
S20=  3.814.697.247.625,2/2
S20 = 1.907.348.623.812.60