How to find the number of terms n in #1+(-2)+(-5)+(-8)...., S"n"=-259#?
2 Answers
The given series belongs to AP.
Its first term
common difference
So sum of n terms
Hence
Explanation:
The sum of a serues is given by
You know that
To remove the
Putting all terms to one side gives
We now that the only two factors of 3 are 1 and 3, so our quadratic is in the form of
So,
As n cannot be negative or a decimal,
The sum of the first 14 terms gives -259.