Find two 2-by-2 invertible matrices whose sum is not invertible.

Do I just start making up matrices, until I find something that works?

Find two 2-by-2 invertible matrices whose sum is not invertible.

Do I just start making up matrices, until I find something that works?

Do I just start making up matrices, until I find something that works?

- stapel_eliz
**Posts:**1738**Joined:**Mon Dec 08, 2008 4:22 pm-
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The determinant for a non-invertible matrix is zero, so these should work:

If you add them, you get:

And any two matrices like that will work, so that's loads of answers right there.

If you add them, you get:

And any two matrices like that will work, so that's loads of answers right there.