Precal Help?

Question

Express the sum without using sigma notation. Simplify your answer where possible.

3
Σ (n − 1)x^(n − 2)
n = 1

Answer 1

Substitute 1, 2 and 3 in for n in the equation (n − 1)x ^n-2 and then add them together.

3
Σ (n − 1)x ^n-2 = (1-1)x ^1-2 +(2-1) x ^2-2 +(3-1)x ^3-2
n = 1

                       =0+ 1x ⁰ + 2x

                        =1+2x

Therfore,

3
Σ (n − 1)x ^n-2 =1+2x
n = 1