x12power 140th power what is the 2nd 3rd 4th term using th

(x1/2power + 1)40th power === what is the 2nd, 3rd, 4th, term using the binomial expansion

Solution

(x^1/2 +1)^40

Gen formula : (r +1)th term = nCr(b)^r(a)^(n-r)

So, 2nd term = 40C1 (1)^1(x^1/2)^39 = 40x^39/2

3rd term = 40C2(1)^2(x^1/2)^38 = 780*x^19

4th term = 40C3(1)^3(x^1/2)^37 = 9880x^37/2