00:02
So when we look at the points p, q, and r, we get f of 0 is 0a plus 0b plus c is equal to negative 3.
00:15
We get f of 1 is equal to 1a plus 1b plus c is 7.
00:24
And f of 4 is equal to 16a plus 4b plus c is equal to 13.
00:35
Cleaning that up, we get c is equal to negative 3a plus b plus c is equal to 7.
00:45
And 16a plus 4b plus c is equal to, let's see, 16.
00:57
Then substituting c is equal to negative 3 in the second equation, we get what? a plus b is equal to 10.
01:07
We get 16a plus 4b is equal to 16 minus 3 is 13.
01:23
No, this was 13 here.
01:25
So we get 13 minus minus 3 is 16.
01:29
And then taking 4 times this second equation, or negative 4 times the second equation, and subtracting it from the third, we get minus 4a minus 4b minus 40.
01:47
So then this is equal to, c is negative 3.
01:54
We still have that.
01:55
We get here, the last equation gives us 16a is equal to negative 24, or a is negative 2.
02:07
And then plugging that in our second equation, a, which is negative 2, plus b is equal to 10.
02:17
So then c is negative 3, b is 12, and a is negative 2.
02:27
So we can write our f of x is ax squared, negative 2x squared, plus bx, 12x, plus c, or minus 3.
02:42
And then, so this was abc.
02:50
Now we want to write this in, complete the square and write this in vertex form.
02:57
So we want to get it as f of x is ax minus h squared, plus k.
03:08
Well, completing the square, negative 2 can be factored out...