Question

Trying to evaluate the following:
Σ i=1,10,4*(-3)^(n-1)
I thought that n=10 so I was left with:
Σ i=1, 10,4*(-3)^(9)
Now what?

Answer 1

The sigma means a summation; you're trying to solve\[\sum_{n=1}^{10} 4*(-3)^{n-1}\]This means that you want to evaluate the expression at n = 1,2,3,...,10 and add the 10 terms together. Ie, \[\sum_{n=1}^{10} 4*(-3)^{n-1} = 4*(-3)^{1-1} + 4*(-3)^{2-1} + 4*(-3)^{3-1} + ... + 4*(-3)^{10-1}\]

Answer 2

I got -393,640.