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# A ball is thrown in air and it's height, h(t) in feet, at any time, t in seconds, is represented by the equation h(t)=−4t2+16t. When is the

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A ball is thrown in air and it's height, h(t) in feet, at any time, t in seconds, is represented by the equation h(t)=−4t2+16t. When is the ball higher than 12 feet off the ground?

Jun 19, 2020

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A ball is thrown in air and it's height, h(t) in feet, at any time, t in seconds, is represented by the equation h(t)=−4t2+16t. When is the ball higher than 12 feet off the ground?

Ein Ball wird in die Luft geworfen und seine Höhe h (t) in Fuß zu jeder Zeit, t in Sekunden, wird durch die Gleichung h (t) = - 4t2 + 16t dargestellt. Wann ist der Ball höher als 12 Fuß über dem Boden?

Hello Guest!

$$h (t) = - 4t^2 + 16t=12\ feets$$

$$- 4t^2 + 16t-12=0$$

$$t= {-b \pm \sqrt{b^2-4ac} \over 2a}$$

$$t= = {-16 \pm \sqrt{(16)^2-4(-4)(-12)} \over 2(-12)}$$

$$t=\frac{-16\pm 8}{-24}$$

$$t_1=\frac{1}{3}\ second\\ t_2=1\ second\\$$

The ball is higher than 12 feet off the ground

between  $$t_1=\frac{1}{3}\ second$$ and $$t_2=1\ second$$.

!

Jun 19, 2020
edited by asinus  Jun 19, 2020