you can do this problem in one of 2 ways: first way which is the easiest is to substitute x=0 then solve for y and substitute y=0 and solve for x:
when u substitute x=0, you get:
y^2+4y=0 subtract 4y from both sides
y^2= -4y divide each side by y
y=-4
now substitute y=0 you get
x^2-14x = 0 add 14x to both sides and divide by x you get
x=14