Tìm x, biết:(x-2) . (x+1) - (x-1) . (x+2) = 0

Tìm x, biết:
a) (x-2) . (x+1) - (x-1) . (x+2) = 0
b) x . (x^2 - 2x) + (x-1) . (x+2) = 0
c) |x-1| + |2-x| = 1
d) 8x - |4x+1| = x+ 2