Question 930432
A penny is thrown up in the air from a building. Its height in feet after x seconds is given by: {{{ -16x^2 +24x+75 }}}
a) when does it reach it's [sic] max height?
It's the vertex of the parabola, at x = -b/2a
x = -24/-32 seconds = 3/4 seconds
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b) what is its max height?
h(x) = -16*(3/4)^2 + 24*(3/4) + 75
= -9 + 18 + 75
= 84 ft
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c) when does it hit the ground?
{{{ -16x^2 +24x+75 = 0}}}
*[invoke solve_quadratic_equation -16,24,75]
Ignore the negative solution.
x =~ 3.041 seconds

For (c) I started to solve it with the quadratic formula but wasn't getting a sensible answer. I'm not sure how to set up the other two.