Answer:
a=8, b=-4
Step-by-step explanation:
set both equal to zero
a: 0 (-1/2)(8)=-4
-1/2y=-4, multiply both sides by the reciprocal of -1/2, which is -2
y=8 when you multiply both sides by -2
b: 4-(0)(0)=-4
when y is 0, the equation become x-0=-4
or x=-4, meaning x must equal -4
