### y= a(x - h)2 + k : the vertex form of a quadratic equation
- a is the constant
- (h,k) is the coordinates of the vertex
- If a<0, we have a function that goes down
- If a>0, we have a function that goes up
- When the vertex form is y = a(x + h)2 + k,
the coordinate of the vertex will be (-h, k)
- When the vertex form is y = a(x - h)2 - k,
the coordinate of the vertex will be (h, -k)