Calculate the speed of $r(t)$

Question

Find the speed of $r(t)=(4t+3,5t−1,5−t)$ at $t=2$.

$\|v(t)\|=\|(4,5,-1)\|=(16+25+1)^{1/2}=(42)^{1/2}=6.48$

How should the $t=2$ be incorporated if there is no variable left when $r(t)$ is derived?

Answer 1

The speed is constant; it has the same value for all $t$.