# Maths

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**Please Help**
.

Express the sum using summation notation:

1 - 1/2 + 1/3 - 1/4 + 1/5 - ... (to 3n terms)

If I'm doing this right so far, with k=1 (the number on bottom of the sigma), the equation after the sigma would be

((-1)^(k+1)) / k

I'd be able to figure out the term on top of the sigma, n, if I knew the value, but I don't understand how to get it because of the way it is worded. Please help, and correct me if what i've done so far is wrong.