Question

Calcular 20 termo da pa (26,31,36,41) e a soma do 20 termo da pa

Answer 1

termo geral
an= a1+(n-1)r
a20=26+(20-1)5
a20= 26+ 100-5
a20= 121

soma dos termos
s20= (26+121).20/2
s20= 147.20/2
s20= 2940/2
s20= 1470