# CAT Quant Practice Problems

Question: Let S denotes the infinite sum $2 + 5x + 9{x^2} + 14{x^3} + 20{x^4} + ...,$where $\left| x \right| < 1$and the coefficient of $x^{n-1} is \frac{1}{2}n(n + 3),(n = 1,{\rm{ }}2,{\rm{ }}...).$Then S equals:
1. $\frac{{2 - x}}{{{{\left( {1 - x} \right)}^{3\,}}}}$
2. $\frac{{2 - x}}{{{{\left( {1 + x} \right)}^{3\,}}}}$
3. $\frac{{2 + x}}{{{{\left( {1 - x} \right)}^{3\,}}}}$
4. $\frac{{2 - x}}{{{{\left( {1 + x} \right)}^{3\,}}}}$

Correct Option:1

## CAT Quant Questions with Video Solutions

CAT Quant Practice Problems