1.C={- 1, -2} or you can write it like this, or c = {x |-3.

2.Cua = {0} indicates that u = {1, 3,0} is x? +3x？ +2x=0 gives x=0,-1, -2.

U = {1, 3,0} So we get the absolute value of (1-2x) =3, and x=- 1, 2.

To sum up, x=- 1.