00:01
So for the chain rule of dzdt, it will be equal to dzdx times dx dx dx d plus dzdy times ydt.
00:23
And so we'll first need to find what dzdx is, it's 6xy cubed, then dxdt, which is equal to 4t cubed.
00:39
I'll try and make that clear as a t.
00:41
And we'll have d z, d, y, equal 9x squared, y squared, and d y d t, will be equal to 2t.
00:56
So now, we'll scroll down a little bit to give ourselves some more space.
01:04
We'll multiply these out, so dz d t is equal to 6xy cubed times 4t cubed plus 9x squared y squared times 2t...