`f(x) = (x - 4)/(x^2 - 7)` Determine the point(s) at which the graph of the function has a horizontal tangent line.
Find the derivative of the function using the Quotient Rule. Set the derivative equal to zero and solve for the critical x value(s). When the derivative is zero the slope of the tangent line will be horizontal to the graph.
Plug in the critical values for x into the f(x) equation.
The tangent line will be horizontal to the graph at points `(1,1/2)` and `(7,1/14).`