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stira [4]
4 years ago
10

Find S18 for geometric series given a5=-6 and a2= -48

Mathematics
1 answer:
Ganezh [65]4 years ago
3 0

an = a1r^(n-1)

a5 = a1 r^(5-1)

-6 =a1 r^4


a2 = a1 r^(2-1)

-48 = a1 r


divide

-6 =a1 r^4

----------------    yields   1/8 = r^3      take the cube root  or each side

-48 = a1 r                     1/2 = r


an = a1r^(n-1)

an = a1 (1/2)^ (n-1)

-48 = a1 (1/2) ^1

divide by 1/2

-96 = a1


an = -96 (1/2)^ (n-1)


the sum

Sn = a1[(r^n - 1/(r - 1)]

S18 = -96 [( (1/2) ^17 -1/ (1/2 -1)]

       =-96 [ (1/2) ^ 17 -1 /-1/2]

      = 192 * [-131071/131072]

 approximately -192

     

       

     

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Help what’s the answer
-BARSIC- [3]
Would be x^2-5-6 so the 0s would be (x-6)(x+1) so 6 and -1
7 0
3 years ago
Can someone help me with questions 1-4
Natalka [10]
1.)
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5 0
3 years ago
Read 2 more answers
I need<br> Help on this one
elixir [45]
The answer is
X=7
Have a nice day <3
5 0
3 years ago
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Maya has 28 apples, 12 oranges, and 8 mangos. She wants to put an equal number of each kind of fruit into baskets so all of the
marysya [2.9K]
12 in each basket.

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Hope this helps!
4 0
3 years ago
Read 2 more answers
How many factors of 2016^2016 have 2016 factors?
Anika [276]
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so the answer is 1  

7 0
3 years ago
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