Question

Find a G.P. for which the sum of first two terms is -4 and the fifth term is 4 times the third term.

Answer 1

a+ar=-4
a(1+r)=-4

$a(r{)}^4=4a(r{)}^2$
$r^2=4$
r = 2

so a= $\frac{-4}{1+2}$ = $\frac{-4}{3}$