a & lt= 0b & gt； 0 or b<0

The conditions of a≤0 and b=0 are met simultaneously.

Or a≤0 or b = 0, as long as one condition is met.

A: x+y ≠ 4 b: x ≠ 2 or y≠2

What is the condition that A is B is not a necessary condition?