What does the second value of `x` mean here?

Question

I looked into this fun math question and I understood his whole explanation except for one part. When he sets $T'(x)=0$, he eventually concludes to $x=8$ and $x=0$. What does the $x=0$ mean? I understand that $x=8$ is the point on the graph where the slope is zero, which indicates (especially when you graph it and look at it) that this is the minimum that we are looking for. But the point $(0, 110)$ is just a point on the sloped part of the curve. What is the significance of this point?

Answer 1

If you are talking about 7:30: It's not $x=0$, it's $$x>0.$$

Normally you would have

$$\begin{align}x^2&=64\\\Longrightarrow~~~x&=\pm \sqrt{64}\end{align}$$ but since $x$ is positive (because it's the length of a line segment where, in this context, negative values don't make sense), i.e. $x>0$, he knows that $x=8$ and $x\neq 8$.