00:01
To start this problem, first let's plug in all of our constants here.
00:05
So we'll have q is equal to 1280 is equal to 40 times c to the 1, or sorry, l to the 1 3rd, times k to the 2 thirds.
00:19
Next, we need to find dk, dl.
00:21
So to find dk, dl, so for part a, we're going to find d, d, dl of both sides of the equation here.
00:33
So we'll take ddl of both of these equations.
00:42
So on the left hand side here, we're just going to get zero.
00:47
Since the derivative of the constant is zero.
00:49
Next, we're going to pull out this 40 first.
00:52
So we'll just have 40.
00:54
And then times we have two functions.
00:57
We're going to take the derivative.
00:59
We're going to need to use product rule to take the derivative.
01:02
So first, d .dl of, well, first we'll do first times the derivative of second, sorry.
01:07
So first times the derivative of the second.
01:12
So the derivative of this with respect to l by the product or sorry the power rule for rational exponents.
01:19
We'll get this.
01:21
And then we're going to need to do times the derivative of k with respect to l by chain rule.
01:29
Next we're going to do, so that was first times the derivative of second.
01:33
Next we're going to add plus second times the derivative of first.
01:37
So plus k to the two thirds times the derivative of the second, which is going to be one -third, l to the negative two -thirds.
01:49
And then now we need to find dkdl solving for this here...