00:01
I would actually start this problem with the equation that they gave you, the 3x minus 9y minus 4 equals 0.
00:11
And the reason why i would work with that is because i would actually add the 9y to the right side, but i'm going to write it this way.
00:18
And then when you divide everything by 9, 3 divided by 9 reduces to 1 3 .5, and then that 4 .9, so i'm just going to leave it.
00:28
But what i really care about is the slope of that tangeline is one -third.
00:32
So double -check my arithmetic there.
00:35
Because then when you go over to the other function defined as x squared minus 1, and when you're asked to find the derivative of that, sorry, it's x squared minus 1x, the derivative of that would be 2x minus 1.
00:56
What we want is the point that gives us a slope of 1 -third...