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siddhartharao77:
is it 115 or 112?
112
Bro, what we have to find...If u know the answer..can u tell,please
find GP
u mean sum of n terms?
yes
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Let the GP be a,ar,ar^2.
Given that sum of first three terms = 14.
a + ar + ar^2 = 14
Given that sum of next three terms = 112
ar^3 + ar^4 + ar^5 = 112.
On Dividing (1) & (2), we get
r^3 = 112/14
r^3 = 8
r = 2.
Substitute r = 2 in (1), we get
a + ar + ar^2 = 14
a + 2a + 4a = 14
a = 14/7
a = 2.
Now,
Sum of n terms = a(r^n - 1)/r - 1
= 2(2^n - 1)/2 - 1
= 2(2^n - 1).
Hope this helps!
Given that sum of first three terms = 14.
a + ar + ar^2 = 14
Given that sum of next three terms = 112
ar^3 + ar^4 + ar^5 = 112.
On Dividing (1) & (2), we get
r^3 = 112/14
r^3 = 8
r = 2.
Substitute r = 2 in (1), we get
a + ar + ar^2 = 14
a + 2a + 4a = 14
a = 14/7
a = 2.
Now,
Sum of n terms = a(r^n - 1)/r - 1
= 2(2^n - 1)/2 - 1
= 2(2^n - 1).
Hope this helps!
:-)
tnq
No thanks
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