Quadratic Equation

Question

A falling object travels a distance given by the formula. d = 2t + 2t^2, where d is measured in feet and t is measured in seconds. How many seconds will it take for the object to travel 85 feet? Round the answer to the 4 decimal places.

Answer 1

85= 2t+2t^2

solve for t

42.5 = t+t^2

t^2 + t -42.5 = 0

t= -1/2 + (1/2)sqr(1^2 -4(1)(-42.5))

t = -.5 +.5sqr(1+4(42.5))

=- .5 + .5sqr(171)

= 6.0383 seconds to reach 85 feet