Given:

Let us consider the equation (1),

Substitute equation (3) in (2), we get

Substitute x=0 and x=-3 in equation (3) we get,

Hence, the solutions are, (0,-6) and (-3,0).
Let us verify this, by substituting (0,-6) and (-3,0) in equation (1), we get
For (0, -6),

For (-3, 0)

Hence, it is verified.