00:01
Okay, here i want to find the slope of the tangent line of these curves, which means find dy by dx.
00:09
So first thing i do, i'll work out dx by dt, and that will be 2t.
00:17
Then i'll find dy by dt, which will be 3t squared minus 1.
00:26
And then to work out what i need, dy by dx, use the chamberl.
00:31
Y by d t times d t by d x in other words that cancel out what's left d y by d x so this then d y by d t is 3 t squared minus one from here and d t by d x is one over that item as d x by d x i want d t by d x so 1 over 2 t so, that means my slope function, divide by dx, is 3 t squared minus 1, divided by 2t.
01:19
Now, when t equals negative 1 is the first requirement, when t is minus 1, i want to work out divide by the x, just plug in negative 1.
01:32
So i get 3 times negative 1 squared is 3 minus 1 is 2 over minus 2.
01:39
So negative 1 is the first answer...