Answer:
y2  =  4ax (opens right, a > 0)
y2  =  -4ax (opens right, a > 0)
x2  =  4ay (opens up, a > 0)
x2  =  -4ay (opens down, a > 0)
Vertex at (h, k) :  
(y - k)2  =  4a(x - h) (opens right, a > 0)
(y - k)2  =  -4a(x - h) (opens right, a > 0)
(x - h)2  =  4a(y - k) (opens up, a > 0)
(x - h)2  =  -4a(y - k) (opens down, a > 0)
Equation of a Parabola in Vertex form
Vertex at Origin :  
y  =  ax2 (opens up, a > 0)
y  =  -ax2 (opens down, a > 0)
x  =  ay2 (opens right, a > 0)
x  =  -ay2 (opens left, a > 0)
Vertex at (h, k) :  
y  =  a(x - h)2 + k (opens up, a > 0)
y  =  -a(x - h)2 + k (opens down, a > 0)
x  =  a(y - k)2 + h (opens right, a > 0)
y  =  -a(y - k)2 + h (opens left, a > 0)
Step-by-step explanation: