# Math Help - Another determinant proof, I'm afraid....

1. ## Another determinant proof, I'm afraid....

^^ That's the one...can someone please help me prove it? I'm not allowed to use the "a1(b2*c3-b3*c2)..." formula. I have to use the silly row-column subtraction/addition arithmetic method, where you have to write r1'=r1-r2, c3'=c3-c2, stuff like that after every relevant step...

2. If you have to show this "the long way", then just do the multiplications, and see what you get. It's long and boring, but pretty straightforward.