( 1+a)(2- 1)^5= 1+a=2
So a= 1
Constant term is mainly composed of two parts.
1 x in the first term) The term multiplied by 1/x in the following binomial expansion is c (5 5,3) (2x) 2 (-1/x) 3 =-40 *1.
So the coefficient is -40.
2) 1/x of the first term is multiplied by x in the next binomial expansion, and the x term is c (5 5,2) (2x) 3 (-1/x) 2 = 80x.
So the coefficient is 80.
Add up these two parts and the result is 40.
So the constant term of this expansion is 40.