Please help me in these problems

Determine which of the four inner product axioms do not hold. give a specific example in the case.

In M22, define <A, B> = det(AB)

Let u and v be in R^2.

define <u, v> = u1v1 - u2v2

axioms:

1) <u, v> = <v,u>

2) <u, v+w> = <u, v> + <u, w>

3) <cu, v> = c<u, v>

4) <u, u> greater than or equal to 0 if and only if u = 0