If `a_1,a_2, a_3, a_4` be the coefficient of four consecutive terms in the expansion of `(1+x)^n ,` then prove that: `(a_1)/(a_1+a_2)+(a_3)/(a_3+a_4)=(2a_2)/(a_2+a_3)dot`

Explanation

To solve the problem, we need to express the coefficients \(a_1, a_2, a_3, a_4\) in terms of binomial coefficients from the expansion of \((1+x)^n\).

### Step 1: Identify the coefficients
The coefficients of the expansion \((1+x)^n\) are given by the binomial coefficients:
- \(a_1 = \binom{n}{r-1}\)
- \(a_2 = \binom{n}{r}\)
- \(a_3 = \binom{n}{r+1}\)
- \(a_4 = \binom{n}{r+2}\)
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