Question

Quantos termos tem a P.G (-8,+4,-2,...,1/4) ?

Answer 1

an=a1.q^n-1

1/4=-8.(-1/2)^n-1

1/4/-8=(-1/2)^n-1

-1/32=(-1/2)^n-1

-2^5=(-2^-1)^n-1

-2^5=-2^-n+1

-n+1=5

-n=5-1

-n=4

n=-4