If a parabola has its vertex at (0,0)(0, 0)(0,0) and directrix x=−5x = -5x=−5, what is its equation?
y2=5xy^2 = 5xy2=5x
y2=10xy^2 = 10xy2=10x
y2=20xy^2 = 20xy2=20x
x2=20yx^2 = 20yx2=20y