00:01
So we have two functions.
00:02
We have a linear function.
00:03
We have f of x is equal to 5x minus 2.
00:08
And then we have a quadratic function.
00:11
We have negative x squared plus 4x minus 1.
00:18
And let's find our f following g of x first, which is f of g of x.
00:30
So we know that we plug x into the g function and it becomes negative.
00:36
The negative, the opposite of the input squared, plus four times the input, minus one.
00:42
And what does that f function do? the f function takes our input and makes it multiplied by five, and then it subtracts away two.
00:51
So our input is negative x squared plus 4x minus 1.
00:56
Let's do a little bit of algebra here and distribute.
00:59
We get minus 5x squared.
01:02
5 times 4 is 20x.
01:06
5 times that negative 1 is negative 5, and then we have to subtract away 2.
01:12
So negative 5x squared plus 20x, and that looks like minus 7.
01:21
And if we do the composition the opposite way, we anticipate getting a different answer, not the same thing.
01:29
So we have g of f of x.
01:32
So now we start with the up of x function.
01:35
And when we plug x into the f of x function, it takes our input, and it makes it five times bigger and then subtracts away two.
01:45
And what does that g function do? well, it does a lot.
01:48
It takes our input and squares it and then takes the opposite of it and adds to it four times our input and then it subtracts away one.
01:57
So we have to input that 5x minus 2 here and that 5x minus 2 here.
02:04
And now we've got some algebra...