∑ (-1)^((n-1)) . 7/9^(n-1)

Question

n=1 to ∞

Answer 1

we have
1 - 7/9 + (7/9)^2 - (7/9)^3 + ...

a = 1 , r = -7/9

sum∞ = a/(1-r)
= 1/(1 - (-7/9) )
= 9/16