Question 441881
y=4x and y=-x^2
we have Y=Y
substitute the values of y
so 
4x=-x^2
so
x^2+4x=0
factorize
x(x+4)=0
so x=0 
or
x+4=0
then x=-4
for x=0
y=4x=4(0)=0    first coordinates (0,0)
for x=-4
y=4(-4)=-16
second coordinates (-4,-16)

note this system has 2 solutions since the equation y=-x^2 is an equation of a parabola which is a curve not a straight line the it cuts the straight line of equation y=4x in 2 points

welcome