Rút gọn: (x + 1)^2 - (x - 1)^2 - 3(x + 1)(x - 1)

1. rút gọn
a. (x+1)^2-(x-1)^2-3(x+1)(x-1)
b. 5.(x+2).(x-2)-1/2.(6-8x)^2+17