Question 189307
Given:
{{{ h=-16t^2+800t }}}
.
a. h = 0
Set h to zero and solve for t:
{{{ h=-16t^2+800t }}}
{{{ 0=-16t^2+800t }}}
{{{ 0=-16t(2t-50) }}}
.
Two possible answers:
-16t = 0
t = 0 seconds (this is at the start)
.
OR
2t-50 = 0
2t = 50
t = 25 seconds (this is at the end)
.
For this problem, the solution would be 50 seconds.
.
b. h = 1
Set h to one and solve for t:
{{{ h=-16t^2+800t }}}
{{{ 1=-16t^2+800t }}}
{{{ 0=-16t^2+800t-1 }}}
{{{ 0=16t^2-800t+1 }}}
Can't factor so you must resort to the quadratic equation.
Doing so will yield two solutions:
x = {49.9987 secs, 0.0013 secs}
.
Details of quadratic solution follows:
*[invoke quadratic "x", 16, -800, 1 ]