## anonymous 3 years ago Quadratics word problem

1. anonymous

An arrow is shot upward from a platform 40 feet high with an initial velocity of 224 ft. per second. its height, h, in feet after t seconds is given by the equation: h= -16t^2 + 224t+40. At what times will the arrow be 824 feet above the ground?

2. anonymous

Am i supposed to plug in 824 for t?

3. anonymous

no, $$t$$ is the time you are looking for you are supposed to replace $$h$$ by 824 and solve for $$t$$

4. anonymous

h is replaced by 824

5. anonymous

$\begin{array}{rcl} h(t) &=& -16t^2 + 224t+40 \\ 824 &=& -16t^2 + 224t+40 \\ 0 &=& -16t^2 + 224t+40-824 \end{array}$ Quadratic formula.

6. anonymous

Ohh ok i see it now.. then you just factor, correct?

7. anonymous

Ummm, you're solving for $$t$$ here. You can factor or use quadratic formula or whatever method you want.

8. anonymous

I see.. thanks!