given a1=[1,-2.0] , a2=[0,1,2] , a3=[5,-6,8] , b=[2,-1,6] determine if b is a linear combination of a1, a2, a3. I put these vectors into an augmented matrix and row reduced. My result was columns 1 and 2 having pivots and the last row being all zeros. Please help me understand how this results in b NOT being a linear combination of a1, a2, a3. The only thing i can think of is that vectors a1, a2, a3 do not span all of R3 and b is not part of the plane that a1, a2, a3 span. If this is the case, please explain how i can see this from the augmented matrix in RREF.