00:01
Okay, the parabola then cuts at negative 4 .0, that's on the left here.
00:05
12 .0 on the right.
00:07
It's on the x -axis.
00:09
On the y -axis, it cuts at 0 -36.
00:13
So i know then that the parabola has to be n -shaped, and a line of symmetry in between 12 and negative 4.
00:24
And it must look something like this.
00:30
I want to find the equation of that parabola.
00:34
Well, let's begin off with where it cuts the x -axis.
00:37
So what's the equation that will give me negative 4 and 12 as the roots? so it's x plus 4 times x minus 12 equals 0.
00:50
That equation has roots of negative 4 and plus 12.
00:55
So that's my starting point for the equation of the parabola.
00:58
So it's x squared.
01:01
If i expand it out, i get 4x minus minus 8x minus 48 equals 0.
01:10
So that equation has the correct roots of negative 4 .12.
01:15
It's not the answer because, as it is now, it's a u -shaped parabola.
01:20
I want n -shaped.
01:22
And also it cuts at 36 here.
01:25
And if i make my x value 0, i get negative 48...