[9.06] A firecracker shoots up from a hill 150 feet high with an initial speed of 110 feet per second. Using the formula H(t) = −16t2 + vt + s, approximately how long will it take the firecracker to hit the ground?

Question

anonymous · Answer

H(t) = 0 when it hits the ground...

anonymous · Answer

s is the initial height, v is the initial speed

anonymous · Answer

okay..?

cgreenwade2000 · Answer

So, plug in 0 for H(t), s =150ft, and v(initial speed) = 100ft/s

cgreenwade2000 · Answer

Then, you will see that there is only one variable to solve for.

cgreenwade2000 · Answer

Sorry, 110 ft/s = v

anonymous · Answer

hmm..im still confused lol sorry. :(

anonymous · Answer

solve the quadratic?

anonymous · Answer

0= −16t^2 + 110t + 150

anonymous · Answer

do i subtract 110 from 150?

anonymous · Answer

would it help if we used x?
$$0=−16∗x^2+110*x+150$$

anonymous · Answer

No just tell me the first thing im suppose  to do please.

anonymous · Answer

should be familiar to you?

cgreenwade2000 · Answer

Don't subtract. The equation is 

0=-16t^2 + 110t + 150

which is in the form you need it to be to solve by using the quadratic formula. 

ax^2 + bx + c =0 

The Quadratic formula is: |dw:1348002636639:dw|