Does the equation specify a function with independent variable x? If so, find the domain of the function. If not, fin a value of x to which there corresponds

Question

Does the equation specify a function with independent variable x? If so, find the domain of the function. If not, fin a value of x to which there corresponds more than one value of y. Y(X+Y)=4

Answer 1

If x = 0, you have y² = 4 so y = ±2  so we have FOUND an x where there exist two possible y values--and that can't be a function (violates vertical line test).