Question

An infinite `G.P.` has `2^(nd)` term `x` and its sum is `4`. Then `x` belongs to
A. `(0,2]`
B. `(1,8)`
C. `(-8,1]`
D. none of these

Answer 1

Correct Answer - C
`(c )` `"Sum"=((x)/(r ))/(1-r)=4` (where `r` is common ratio)
`x=4r(1-r)`
`=4(r-r^(2))`
For `r in (-1,1)`
`r-r^(2)in(-2,(1)/(4)]`
`impliesx in (-8,1]`