00:01
All right, here's a function that models a company's total sales based on thousands of dollars spent on advertising.
00:08
And total sales could be measured in dollars or a number of units or whatever they want to measure by.
00:15
And then amount spent on advertising is between zero and $200 ,000 because we're in thousands of dollars.
00:23
Okay, so first they want us to find the rate of change.
00:26
So s prime, so keep it a capital s.
00:30
Okay, so we're using the power rule, so minus 0 .006, multiplying by 3x squared, plus 1 .2 x to the 1 plus 1, and derivative of 500 is 0.
00:44
So there's the rate of change, and they're asking, is the money increasing, or are the sales increasing faster when we're spending $100 ,000 or $150 ,000? so we're comparing s prime of 100 and s prime of 150.
01:07
So let's see what happens.
01:09
100, i'm moving this four decimal places.
01:12
So that's negative 60 plus 120 plus 1...