Answer:
2 seconds.
Step-by-step explanation:
Given [tex]d=4t+16t^{2}[/tex] and d = 72 ft
We need to solve [tex]72=4t+16t^{2}[/tex]
[tex]4t+16t^{2}-72=0[/tex]
[tex]4t^{2}+t-18=0[/tex]
[tex]4t^{2}+9t-8t-18=0[/tex]
[tex]t(4t+9)-2(4t+9)=0[/tex]
[tex](t-2)(4t+9)=0[/tex]
[tex]t-2=0,4t+9=0[/tex]
[tex]t=2,t=-\frac{9}{4}[/tex]
Since, time can not be negative, so the required time is t = 2 seconds.
