00:01
So in this problem, we're told that since 2013, the annual revenue earned by amazon can be modeled by the given function r of x.
00:08
So x is the number of years since 2013, and r of x represents the annual revenue in terms of billions of dollars.
00:15
So the first thing we want to do is we want to find the value of r of 4 minus r of 1, all divided by 4 minus 1.
00:23
So the first thing we need to do is we need to find r of 4.
00:26
Well, that means we're substituting in 4 and 4x in our function.
00:28
So we're going to have 1 .2 times 4 squared plus 11 .62 times 4 plus 62 .22.
00:36
So now we'll use our calculator.
00:39
So we're going to have 1 .2 times 4 squared plus 11 .62 times 4 plus 62 .22.
00:47
And that would equal to 127 .9.
00:50
So that would mean that r4 is the revenue after for four years since 2013, which is in the year 2017.
00:58
Now, the next thing we need to do is we need to find r1.
01:01
So we're going to substitute a 1 for us.
01:03
So we're going to have 1 .2 times 1 squared plus 11 .62, nope, let's put the 2 in there, times 1, plus 62 .22.
01:13
So if we do 1 .2 times 1 squared plus 11 .62 times 1 plus 62 .22, that would equal to 75 .04.
01:24
So let's go ahead and put that in here.
01:25
All right, well, remember, r represents the revenue and x is the number of years since 2013.
01:32
So because x is equal to 1, that would mean that that would represent the year 2014...