[tex]\displaystyle\bf\\5)\\\\Otvet : a) \ y=\frac{3x-4}{x^{2} } \\\\\\6)\\\\S(t)=6-4t+t^{2} \\\\\\V(t)=S'(t)=6'-4\cdot t'+(t^{2} )'=0-4\cdot 1+2t=2t-4\\\\\\V(t)=10\\\\\\2t-4=10\\\\\\2t=14\\\\\\\boxed{t=7}[/tex]