Matrices transformations

[Pking time 2]

Transform the unit square with vertices A(0,0), B(1,0), C(1,1) and D(0,1) by the matrix E = [3 0 ] E is a 2 by 2 matrix. Please help I dont understand this question
                                                                                                                                                0 3

[kinslayer]

Turn each of the four points into 2-d vectors and then multiply them on the left by E.

You can use the fact that E is 3 times the identity matrix. The identity matrix is the "1" matrix (hence identity) which means that I*M = M*I = M for any M of the right size.

So the transformation is just dilation by a factor of three. The four vertices of the new square are A(0,0), B(3,0), C(3,3), D(0,3).