Question

Find the 11th partial sum of the summation of negative 7i plus 22, from i equals 1 to infinity.

-220
400
550
-700

Answer 1

The answer is -220
What you do is take -7 and multiply that by (1+2+3+4+5+6+7+8+9+10+11) and then after that add 11 again and multiply it by 22. It would look like this.

-7 x (1+2+3+4+5+6+7+8+9+10+11) +11 x 22

Simplify that to -7 x 66 +11 x 22

now multiply -7 and 66 to get -462

-462 +11 x 22

multiply 11 and 22

-462 + 242

and your final answer will be -220