i hope you can help i am soooo stuck here goes:

a)

A= 0 1	B= 1 1	c= 2 5
   0 2	   3 4	   3 4

Evaluate AB and Ac (which I can do)

then

b)
I need to prove that if the matrix A is inverible and AB =AC, then B = C. Why does this not contradict what happened in part a)?

thanking you
vikki

If A is invertible and AB=AC then B=C.

This is true because if A is invertible,Êyou multiply both sides of the equation AB=AC from the left by A inverse to get IB=IC which simplifies to B=C sinceÊI is the identity matrix.

This does not contradict what you did in part (a) (where AB=AC but B does not equal C) because the matrix A in your problem is not invertible (because of the column of zeroes). The words "if A is invertible"Êare very important in the statement underlined above.

Leeanne