Hello, The ratio of this geometric sequence is -6. [tex] u_{1} =-4\\
u_{2} =-4*(-6)=24\\
u_{3} =-4*(-6)^2=-4*36=-144\\
...\
u_{7} =-4*(-6)^6=-186624\\\\
-4+(-4)*(-6)+(-4)*(-6)^2+(-4)(-6)^3+...+(-4)*(-6)^6\\\\
=-4(1+(-6)+(-6)^2+(-6)^3+...+(-6)^6)\\\\
=-4*(\frac{-6)^7-1}{(-6)-1} =\frac{-4}{-7}*(-279936-1)\\\\
=-159964
[/tex]
