Question

to find x you plug in the slope into the derivative right?

Answer 1

perhaps you mean
"to find the slope you plug your value in for x in the derivative"

Answer 2

okay so the questions is "find all points x,y on the curve where the line tangent to the curve has slope -1/2. so the curve given is y=(2x-5)/(x^2-4) and the derivative was [-2(x-4)(x-1)]/[(x^2-4)^2]