How many points do you need to determine the equation of a parabola?

1 Answer
Oct 24, 2015

2: the vertex and another point

Explanation:

the vertex gives the values #(h,k)#
another point gives #(x,y)#
these can be plugged into vertex form, #y=a(x-h)^2 +k#

to get the equation of a parabola in standard form:
once the four values are plugged into vertex form, the equation can be solved for the variable #a#

#b# can then be found using #x=((-b)/(2a))#

to find #c#, plug in the #a# and #b# values into #y=ax^2+bx+c# as well as the point from before (for #x# and #y#) and solve it

finally, plug the #a#, #b#, and #c# values into #y=ax^2+bx+c# and you have your equation in standard form

there are probably other ways to do this, but overall, a minimum of 2 points is needed