Question

the sum of 3/5x + 2/3 x - - 4/5 x is​

Answer 1

Answer:

Let S=1+3x+5x

2

+7x

3

......∞

Multiplying both sides by a, we get

Sx=0+x+3x

2

+5x

3

.......∞

Subtract both eqns, we get

S(1−x)=1+2(x+x

2

+x

3

.......∞)

Clearly, the series in the bracket is a G.P. with common ratio =x

∴S(1−x)=1+

1−x

2x

=

1−x

1+x

⇒S=

(1−x)

2

1+x

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