## anonymous one year ago Help for a medal?

1. anonymous

A firecracker shoots up from a hill 160 feet high, with an initial speed of 90 feet per second. Using the formula H(t) = -16t2 + vt + s, approximately how long will it take the firecracker to hit the ground?

2. Liv1234

Are there any options with this question?

3. anonymous

Yeah, the options are Five seconds Six seconds Seven seconds Eight seconds

4. Liv1234

5. Liv1234

By the way, I'm still here I'm just working on solving it so I can help you.

6. anonymous

Alright

7. Liv1234

Multiply out everything, then move everything over to the right except for "y". If you get something in the form of y = ax^2 + bx + c, where 'a' is not zero, then it's a quadratic equation. 2) Multiply out the right until you get something in the form of y = ax^2 + bx + c, then look at what 'a' would be. 3) y = ax^2 + bx + c is going to be the graph of a parabola. If a > 0, then it opens upwards and the vertex shows the minimum value for y. If a < 0, then it opens downwards, and the vertex shows the maximum value for y. 4) Subtract 24x from both sides, then factor out 8x. 5) See #4

8. anonymous

Why delete it? I was in the middle of reading it D:

9. jim_thompson5910

10. jim_thompson5910

$\large \text{A firecracker shoots up from a hill } {\color{red}{\text{160 feet high}}},\\ \large\text{with an }{\color{green}{\text{initial speed of 90 feet per second}}}.\\ \large \text{Using the formula } H(t) = -16t^2 + vt + s,\\ \large \text{approximately how long will it take the firecracker to hit the ground?}$ From that info, we can pull out $\large \text{Initial Height: }{\color{red}{ s = 160}}$ $\large \text{Initial Velocity: }{\color{green}{ v = 90}}$ So the expression $\large -16t^2 + {\color{green}{v}}t + {\color{red}{s}}$ turns into $\large -16t^2 + {\color{green}{90}}t + {\color{red}{160}}$ Hopefully this is making sense so far?

11. jim_thompson5910

but it's fixed now

12. jim_thompson5910

From here you need to solve $\Large -16t^2 + 90t + 160=0$ for t. Use the quadratic formula to do so

13. anonymous

Alright, I can handle it from here. Sorry for the delay, the pizza man came :D

14. jim_thompson5910

That's ok. Let me know what solutions for t you get.

15. anonymous

If I remember too then I will!