00:01
We have a profit function here as a function of x and y.
00:05
We'd like to find the values of x and y that maximize profit.
00:10
It's just to say we want a critical point of this p function here.
00:15
It's going to be where px is equal to 0, and py is also equal to 0, where x and y are the partial derivatives.
00:24
Let's do that real quick.
00:26
Px is equal to, see, the x derivative of 2 ,000 is 0.
00:29
This is constant.
00:31
So that's going to be plus 30 minus, let's see, 4 times x is not there by the power rule.
00:42
And then y is constant with respect to x, so both of these just go to 0.
00:46
So px is 30 minus 4x.
00:50
If this is equal to 0, then that means 4x is equal to 30.
00:56
So x is equal to 30 over 4, which is 15 over 2, which, if you like, is 7 and 1 half.
01:06
So that's neat.
01:08
Py now, we could differentiate.
01:11
Again, the constant differentiates to 0.
01:13
But now these x terms go away.
01:15
We just get 100 minus 2y.
01:19
If this is 0, then y must be 50, because 2y is 100...