A in b can be equal to 0, 1, 2, then 2a = 0, 2, 4, that is, b = {0, 2, 4};

So a ∩ b = {0 0,2}

2。

F(x) is an even function,

When x < 0, f (x) = f (-x) = (-x) (1+x) =-x (1+x).