If in the expansion of `(a+b)^n\ a n d\ (a+b)^(n+3)` , the ratio of the coefficients of second and third terms, and third and fourth terms respectively are equal, then `n` is a. 3 b. 4 c. 5 d. 6

Explanation

Coefficients of the 2 nd and 3rd terms in `(a+b)^{n}` are `\ ^{n} C_{1}` and `\ ^{n} C_{2}`


Coefficients of the 3 rd and 4 th terms in `(a+b)^{n+3}` are `\ ^{n+3} C_{2}` and `\ ^{n+3} C_{3}`


Thus, we have


`frac{\ ^{n} C_{1}}{\ ^{n} C_{2}}=frac{\ ^{n+3} C_{2}}{\ ^{n+3} C_{3}}`


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