How to calculate the exact values of c and d Draw the function $f(x)= x^3-4x^2-13x+10$ into a cartesian plane. If the exact length of that curve from point $P(5,-30)$ to point $Q(c,d)$ is $18$ (with $c>5$), I have no idea how to calculate the values of $c$ and $d$ using the formula $(dx)^2+(dy)^2$. How to approximate the exact values of $c$ and $d$ ? What is the values of $c$ and $d$ (exactly) ?

I did an exhaustive manual calculation using wolfram alpha, and if I'm not making any mistakes,  the value of $c$ up to 6 digits precision is $5.61680$....
