Show that the range of the linear operator defined by the equations

w1 = 4x1 - 2x2

w2 = 2x1 - x2

is not all of R2, and find a vector that is not in the range.

Ok I can easily show the range is not all of R2 by finding the determinant to be zero... but how the vector which is not in the range? I know this is probably really easy.