(31x+1) ‌=(x+1)49(31x−19+x−20) ‌=31x−19(x+1)49+x−20(x+1)49 For constant term x0 ∴ Constant term in 31x−19(x+1)49 i.e., x−19⋅xk=x0⇒k=19 ∴ Constant term =31‌49C19
Constant term in x−20(x+1)49 i.e., x−20⋅xk=x0⇒k=20 ∴ Constant term =1×‌49C20 ∴ Sum of constant term =31‌49C19+‌49C20 =3049C19+‌49C19+‌49C20 =30⋅‌49C19+‌50C20