The derivative of y with respect to x is going to be equal to 3 times y minus x squared minus 2x, all of that over this stuff, 3 times y minus x squared. And we can leave it just like that for now. So what is the derivative of y with respect to x? What is the slope of the tangent line when x is 1 and y is equal to 4? Well, we just have to substitute x is equal to 1 and y equals 4 into this expression. So it's going to be equal to 3 times 4 minus 1 squared minus 2 times 1, all of that over 3 times 4 minus 1 squared, which is equal to 4 minus 1 is 3. You square it, you get 9.