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Mathematics
Mathematics
Problem
Let
a
a
a
be the first term and
r
(
≠
1
)
r\,(\neq 1)
r
(
=
1
)
the common ratio of a geometric progression. a. Write the sum
S
n
S_n
S
n
of the first
n
n
n
terms in expanded form. b. Prove that
S
n
=
a
(
r
n
−
1
)
r
−
1
.
S_n=\frac{a(r^{n}-1)}{r-1}.
S
n
=
r
−
1
a
(
r
n
−
1
)
.
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