Tuesday

July 29, 2014

July 29, 2014

Posted by **Rachel** on Monday, May 7, 2012 at 1:58pm.

Sn=189

Find n for the given sum if the geometric series

- Algebra 2 -
**Reiny**, Monday, May 7, 2012 at 2:08pmlooks like

a = 5 and r = -1/2

so 5((1 - (-1/2)^n)/(1-(-1/2)) = 189

1 - (-1/2)^n = 56.7

(-1/2)^n = -56.7

since we know that n must be a whole number and for the above to be true, n must be odd

so we could solve

(1/2)^n = 56.7

using logs,

n = log 56.7/log .5 = a negative

No answer to your question !!!

There is something bogus about your question.

(your last sentence appears incomplete)

**Related Questions**

Math - Find a1 in a geometric series for which Sn=189,r=1/2,and an=3. Sn=a1(1-r^...

algebra(check) - 1)Find a1 in a geometric series for which Sn=300,r=-3,and n=4 a...

algebra - 1)Find a1 in a geometric series for which Sn=300,r=-3,and n=4 a.15 b....

algebra - 1)Find a1 in a geometric series for which Sn=300,r=-3,and n=4 a.15 b....

algebra - 1)Find a1 in a geometric series for which Sn=300,r=-3,and n=4 a.15 b....

CALC II - Determine the convergence of the following series using the nth-...

Algebra 2 - How would I find the sum of the geometric series given? 1/5 - 1/25...

Algebra - Two questions I need help with. Find the indicated partial sum using ...

sum geometric series - what is the sum of geometric infinite series 3/2+ 9/16+ ...

math - 1)Find a1 in a geometric series for which Sn=300,r=-3,and n=4 A)15 B)15/2...