[Linear algebra] linear combinations

Determine if b is a linear combination of a1 a2 and a3 (each a 3 by 1 matrix) a1 = [1,-2,0] a2 = [0,1,2] a3 = [5,-6,8] b = [2,-1,6]. My text book says it is a linear combination but I'm getting an inconsistent matrix and im wondering what I'm doing wrong