00:01
Okay, this function is a parabola and i can see negative 4 here, which means an n -shaped parabola like this.
00:10
And here's the vertex i want to find.
00:12
And this line of symmetry down the middle has the equation x equals negative b over 2a.
00:20
The a is negative 4, the b is minus 10, the c is 6.
00:27
So what we have here then is minus.
00:31
Minus 10 and twice a is minus 8.
00:37
So that becomes minus 1 .25.
00:50
That will be minus 5 over 4.
00:52
Yep, that's right.
00:53
And to find the y value, just plug it into the formula.
00:57
I want to work out.
01:02
F of minus 1 .25.
01:05
What do i get? negative 4 minus 1 .25.
01:14
Minus 10x minus 10 minus 1 .25 plus 6.
01:29
So what i get here? let's have a look.
01:34
1 .25 squared times minus 4.
01:41
So i have here minus 6 .25 plus 12 .5 plus 6 .5 plus 6.
01:55
So that becomes 12 .25.
02:07
So the answer here is then is minus 1 .25 and 12 .25...