SOLUTION: Please help me, I don't understand I've tried it and came up with -1874571.4 but I know the answer is 714.5. Could you please show me the steps... *** Find the partial sum of the

Question 877110: Please help me, I don't understand I've tried it and came up with -1874571.4 but I know the answer is 714.5. Could you please show me the steps...
*** Find the partial sum of the geometric series. S9 for 1000-400+160-64+...
Answer by rothauserc(4718) (Show Source): You can put this solution on YOUR website!
S9 = a +ar +ar^2 +ar^3 +ar^4 + .... +ar^9, where r is the common ratio
S9 = a(1 - r^9) / (1 - r)
We are given 1000 -400 +160 -64 +
To find r, we divide the second term by the first
r = -400 / 1000 = -2/5
S9 = 1000(1 -(-2/5)^9) / (1 -(-2/5)
S9 = 1000(1 -(-0.000262144)) / 1.4
S9 = 1000 * 1.000262144 / 1.4
S9 = 714.47296

RELATED QUESTIONS
a water park charges $12 dollars for admission and $5 for parking. Write an inequality to (answered by josgarithmetic,amalm06)

Can you help me with this equation. My son came up with the wrong answer and when i used... (answered by funmath)

In how many ways could five different envelopes be distributed into three mailboxes? The... (answered by ikleyn)

Please help me solve this equation: 1-r= -5 I tried it and i got this: 1-r =-5 -1 (answered by jim_thompson5910)

Please help me with this problem. Factor Completley. 6w^6-40w^5+50w^4 this is the... (answered by sarah_adam)

I've been struggling with this problem. 13n-12 ≤ -8+9n I don't know how to solve... (answered by CubeyThePenguin,josgarithmetic,ikleyn)

What would be the solution for x in the rational equation: x^2/(x-3) = (x+2)/(2x-5) (answered by josgarithmetic)

Simplify (be sure to rationalize all denominators) 12. x^(3/4) + 5/[x^(1/4)] (you may (answered by fractalier)

i have to graph y=x(1+x)^2 but what i don"t understand is why is it when you foil it in... (answered by Fombitz)