Question

Someone explain how to do this step by step?

Answer 1

Hello,

Let's
`v_(1)\mbox{ the speed of David },\ t_(1) \mbox{ the time of David}\\ v_(2)\mbox{ the speed of Sione },\ t_(2) \mbox{ the time of Sione}\\\\ v_(2)=v_(1)+4\ (1)\\ t_(2)=t_(1)- (1)/(2)\ (2) \\ 150=v_(1)*t_(1) \ (3)\\ 150=v_(2)-t_(2) \ (4)\\ (3) \ and \ (4)==\textgreater\ 150=v_(1)*t_(1)=(v_(1)+4)*(t_(1)- (1)/(2) )\\ ==\textgreater\ 8*t_1-v_1=4==\textgreater\ t_1= (v_1+4)/(8)\ (5)\\ (3)\ and\ (5)==\textgreater\ v_1*(v_1+4)/(8)=150\\ ==\textgreater\ v_1^2+4v_1-1200=0\\`


`\Delta=16-4*(-1200)=4816\\ v_1= (-4\pm 4√(x) 301)/(2) \\ v_1=-2+ √(301) =32.6987031... (km/h) \ since \ (v_1\ \textgreater \ 0)\\`