SOLUTION: PLEASE HELP ME The sum of the geometric series 42-7+(7/6)...+42(-1/6)^9 is approzimately a. 34.833333 b. -0.857 c. 35.9999994 d. -35.99999643 THANK YOU

Algebra ->  Sequences-and-series -> SOLUTION: PLEASE HELP ME The sum of the geometric series 42-7+(7/6)...+42(-1/6)^9 is approzimately a. 34.833333 b. -0.857 c. 35.9999994 d. -35.99999643 THANK YOU       Log On


   

Question 144243: PLEASE HELP ME
The sum of the geometric series 42-7+(7/6)...+42(-1/6)^9 is approzimately
a. 34.833333
b. -0.857
c. 35.9999994
d. -35.99999643
THANK YOU

Answer by nabla(475) About Me  (Show Source):
You can put this solution on YOUR website!
Let's put this in symbols:
sum%28+%28-1%2F6%29%5Ek%2A42%2C+k=0%2C+k=9+%29
The sum is simplified by using:
a%281-r%5E%28n%2B1%29%29%2F%281-r%29
Where a= first term, r= common ratio, n= top kth number. So,
a=42; r=(-1/6); n=9.

42%281-%28-1%2F6%29%5E%289%2B1%29%29%2F%281-%28-1%2F6%29%29
=
%286%2F7%2942%281-%28-1%2F6%29%5E%2810%29%29%29
=
36%281-%28-1%2F6%29%5E%2810%29%29%29
Use a calculator for the answer of:
=35.9999994; c.