# Using the vertex form, how do you solve for the variable a, with the points (3,1) the vertex and(5,9)?

##### 1 Answer

May 30, 2015

The answer depends upon what you intend by the variable

If the vertex is

and another point on the parabola is

Then the vertex form can be written

which, with

#8 = 2m#

# m =4)#

and the vertex form is

#y = 4(x-3)^2+1#

**Option 1:** (less likely option, but possible)

The vertex form is sometimes written as

in which case

**Option 2:**

The generalized standard form of a parabola is usually written as

in which case