the function D(t)=17t^2-140t gives the distance a car going a certain speed will skip in t seconds. find the time it would take for the car to skid 160 feet.

Question

i need help with this word problem i do not know how to even start it please help......this is very confusing to me and i cant read very well. 

Answer 1

D(t)=17t^2-140t

skid 160 feet

160=17t^2-140t

17t^2-140t-160=0

use the quadratic formula

[140±√(140^2+4*17*160)]/2*17

[140±√(19,600+10,880)]/34

[140±√30,480]/34

(140+174.585)/34 (you don't want a negative answer)

314.585/34

9.2525 seconds (round as needed)