taking the given series as S =1+ (1+a)x+(1+a+a^2)x^2+(1+a+a^2+a^3)x^3+----------- -S*x = -x(1) - x((1+a)x)+ - x((1+a+a2)x^2) -x((1+a+a2+a3)x^3)+---- ---------------------------------------------------------------------------------------------------------------------- S(1-x) =1 + ax + a^2x^2 +a^3x^3......................
now this is an GP so sum upto infinity of an GP is 1/(1-r) where r is common ratio here the common ratio is ax so
Moderation Team
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