I have the matrices R=[s,s;0,s] and A=[0,s;0,0]. Now, A is the ideal and it is also supposed to be the Kernel, as I am trying to show that R/ker f is isomorphic to SxS. So, when trying to show A is the kernel, can I just show it takes everything and brings it to the additive identity or is this wrong b/c there is multiplication and addition in rings?