Digital Image processing problem:

In general, do affine transformations commute? That is, given two affine transformations T1 and T2, does the transformation TiT2 give the same result as T2T1? (T1 and T2 are the matrix representations of the transformations.) If not, provide a counter example. That is, provide affine transformation matrices T1 and T2 such that a point mapped by T1T2 is different from the same point mapped by T2T1