( 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.