Log in

View Full Version : College Algebra


cgold1
Nov 28, 2008, 08:48 PM
This college algebra class is kciking my butt. I am trying to solve an application problem which wants to know how high a rocket will travel at t seconds using
s(t)=-16t^2+96t=32 ft

Here is how I tried to solve it:

= 16(-t^2+6t+2)
= 16(-6+/-sqt 6^2-4*-1*2 ) / 2*-1
= 16(-6 +/- sqt 36-(-8) )/-2
= 16(-6 +/- sqt 44) /-2
= 16(-6 +/- 2 sqt 11) / -2
= 2*16(-3 +/- sqt 11) / -2
= 32(-3 +/- sqt 11) / -2
= -16(-3 +/- sqt 11)

I came up with -16 (-3+/-sqt 11)

Please point me in the right direction... Thank you in advance

galactus
Nov 29, 2008, 01:33 PM
You are on the right track. Except, get rid of that 16. It's not really needed.

I assume then you are solving the quadratic for t?

-16(t^{2}-6t-2)=0

t^{2}-6t-2=0

We can complete the square or use the quadratic formula.

Completing the square, we get:

(t-3)^{2}-11=0

Now, solve for t and we get what you have. t=\sqrt{11}+3, \;\ t=-\sqrt{11}+3