Answer:
3.81 s
Step-by-step explanation:
Let's consider the following formula that represents the journey of a falling object.
d = 3 t + 5 t²
where,
- d is the distance measured in feet
- t is the time measured in seconds
We can find the time that it will take to travel 84 feet by replacing d = 84 in the equation.
84 = 3 t + 5 t²
5 t² + 3 t - 84 = 0
We have a = 5, b = 3 and c = -84. We apply the second grade solving formula.
[tex]x_{1,2} = \frac{-b \pm \sqrt{b^{2}-4ac} }{2a} = \frac{-3 \pm \sqrt{3^{2}-4(5)(-84)} }{2(3)}[/tex]
x₁ = 3.81 and x₂ = -4.41
Since the time cannot be negative, the answer is t = 3.81 s
