Answer
$x=1+\sqrt 2$ and $x=1-\sqrt 2$
Work Step by Step
The derivative of a function is the slope of the tangent line of that curve. So if we want points where the tangent line is horizontal, its slope must be 0.
Then we have to derivate the function using the quotient rule, and after that equal this derivative to zero and solve the quadratic equation, getting the solution. All of that is done on the image below.
