Question

Linear Algebra : find a subset F of R^2 contains OR^2=(0,0) s.t F is not subspace.

Answer 1

Pretty much anything that is not a line or the xy plane will work...

Answer 2

give me an example

Answer 3

Okay, let F be all (x, y) s.t. y <= 0. You can easily prove this is not a subspace, but it's a subset of R^2.

Answer 4

got it tanks