Ok so on this weeks home work there is the following question

Let A =

2 1

1 2

Let B =

1 1

1 -1

Part 1 says compute $\displaystyle B^{-1}$ which i found to be

$\displaystyle B^{-1}$=

0.5 0.5

0.5 -0.5

The next part is the problem it asks to show that $\displaystyle B^{-1}AB $is a diagonal matrix

Having multiplied $\displaystyle B^{-1}AB $ i dont get i diagonal matrix i get

2 1

1 2

I have checked and re-checked all my working and cant see where im going wrong?

Any help most appreciated