If the 6th, 7th, 8th terms in the expansion of `(x+ a)^n` be 112, 7 and 1/4 find x, y and n.

Explanation

The 6 th, 7 th and 8 th terms in the expansion of `(x+a)^{n}` are `\ ^{n} C_{5} x^{n-5} a^{5}, C_{6} x^{n-6} a^{6}` and `\ ^{n} C_{7} x^{n-7} a^{7}`.


According to the question,


`\ ^{n} C_{5} x^{n-5} a^{5}=112 `


`\ ^{n} C_{6} x^{n-6} a^{6}=7 `

`\ ^{n} C_{7} x^{n-7} a^{7}=frac{1}{4}`
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