JEE Math Practice Question
Let $$S = 2 + {6 \over 7} + {{12} \over {{7^2}}} + {{20} \over {{7^3}}} + {{30} \over {{7^4}}} + \,.....$$. Then 4S is equal to
- A.$${\left( {{7 \over 3}} \right)^2}$$
- B.$${{{7^3}} \over {{3^2}}}$$
- C.$${\left( {{7 \over 3}} \right)^3}$$
- D.$${{{7^2}} \over {{3^3}}}$$
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