Respuesta :
Answer:
7
Step-by-step explanation:
Solving a quadratic equation:
Given a second order polynomial expressed by the following equation:
[tex]ax^{2} + bx + c, a\neq0[/tex].
This polynomial has roots [tex]x_{1}, x_{2}[/tex] such that [tex]ax^{2} + bx + c = a(x - x_{1})*(x - x_{2})[/tex], given by the following formulas:
[tex]x_{1} = \frac{-b + \sqrt{\Delta}}{2*a}[/tex]
[tex]x_{2} = \frac{-b - \sqrt{\Delta}}{2*a}[/tex]
[tex]\Delta = b^{2} - 4ac[/tex]
In this question:
The height of the rock after t seconds is given by the following equation:
[tex]H(t) = -16t^2 + 96t + 112[/tex]
How long will it take in seconds for the rock to hit the ocean?
This is t for which:
[tex]H(t) = 0[/tex]
So
[tex]-16t^2 + 96t + 112 = 0[/tex]
Simplifying by -16
[tex]t^2 - 6t - 7 = 0[/tex]
So a quadratic equation with [tex]a = 1, b = -6, c = -7[/tex]
[tex]\Delta = b^{2} - 4ac = (-6)^2 - 4*1*(-7) = 36 + 28 = 64[/tex]
[tex]t_{1} = \frac{-(-6) + \sqrt{64}}{2*1} = 7[/tex]
[tex]t_{2} = \frac{-(-6) - \sqrt{64}}{2*1} = -1[/tex]
Since time is a positive measure, it will take 6 seconds for the rock to hit the ocean, and the answer is 7.
