SOLUTION: I need help on this homework problem. Thank you for any help you can provide. a1=1 r=-1 find s20 I keep getting 1 as the answer but the answer is 0. what am I missing?

SOLUTION: I need help on this homework problem. Thank you for any help you can provide. a1=1 r=-1 find s20 I keep getting 1 as the answer but the answer is 0. what am I missing?

Algebra.Com

Question 63561: I need help on this homework problem. Thank you for any help you can provide.
a1=1 r=-1 find s20
I keep getting 1 as the answer but the answer is 0. what am I missing?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
a1=1 r=-1 find s20
---------
S(n)= a(1)[r^(n+1)-1]/ [r-1]
S(20)= 1[[(-1)^(21)-1]/[-1-1]
S(20)= [-1-1]/[-1-1]=1
You are correct.
Cheers,
Stan H.
RELATED QUESTIONS
Hello, I am stuck with this problem and cannot seem to find any help. I need to find... (answered by ewatrrr)

Hello I need help solving a geometric sequence, I need to find S20 for the series -1 + -3 (answered by ikleyn)

Find a1 if d = 4, a20 = 82, and S20 = 880. A.) 2 B.) 4 C.) 6 D.) 60 is this (answered by stanbon,ikleyn)

Special Sequences help? 1. Find the 4th term if the sequence in which a1 = 2 and an+1 =... (answered by jim_thompson5910)

I need help figuring out how to write out this problem. The question reads: The larger of (answered by scott8148)

Could you please help me with the following problem? I am supposed to solve this... (answered by jim_thompson5910)

Hi, I need help factoring the following equation: (x-2)^3-1 I have taken it to this... (answered by nyc_function)

I need help on a word problem I think I have the right answer I just need confirmation.... (answered by bucky,josmiceli)

I have tried this problem, but I keep getting a remainder. Can you help please?... (answered by rapaljer)