First, work out the slope of the secant line :
Now that you know the slope of the secant line, you can derivate and find a derived point of which has the same slope as the secant line.
The derivate of is :
Now you want a slope of , right ? Therefore, you will want to solve the derivative like this :
Which gives :
Now solve this simple equation :
Factorize this (and by the way, on right-hand-side) :
Easy solve :
Now you know that the points that have x-coordinate and have a slope of on the first function. Substitute back into the first function to find their y-coordinate :
Let's conclude : when or , the tangent to this point of the function has a slope of , which is equal to the slope of the secant line .
So, the solutions are the points and .