Originally Posted by

**brumby_3** What is the inverse of:

[3 7]

[1 3]

I've tried working it out, but I keep getting the wrong answer.

Here's my working out:

[3 7 1 0]

[1 3 0 1]

Divide row 1 by 3

[1 2.3 0.3 0]

[1 3 0 1]

Row 1 minus (1 x row 1)

[1 2.3 0.3 0]

[0 1 -0.43 1.43]

Row 2 divided by 0.7

[1 2.3 0.3 0]

[0 1 -0.43 1.43]

Row 1 minus (2.3 x row 2)

[1 0 1.289 -3.289]

[0 1 -0.43 1.43]

The answer is supposed to be:

[3/2 -7/2]

[-1/2 3/2]

But my answers don't match the ones I got above even when I try and change the decimals to fractions.

Help would be much appreciated. Sorry if the matrices look messy, I hope you get the idea.