Juan recorded his brother bungee jumping from a height of 1100 feet. At the time the cord lifted his brother back up, he was 76 feet above the ground. If Juan started recording as soon as his brother fell, how much time elapsed when the cord snapped back? Use f(t)=-16t^2+c, where c is the height.

Question

anonymous · Answer

f(t)= -16t^2+1100

at t=x
f(x) = 76

so solve for x
76=-16x^2+1100

anonymous · Answer

I got x = 8i?

anonymous · Answer

double check your math

anonymous · Answer

76=-16x^2+1100
-1100+76=-16x^2
-1024=-16x^2

divide by -16
64=x^2

anonymous · Answer

I did: 
76=-16x^2+1100
-1100         -1100
-1024=16x^2
/16       /16
-64 = x^2
-8i  = x

anonymous · Answer

you cant just get rid of the negative sign in front of the 16

anonymous · Answer

Oh crap i totally didnt see the - sign. My bad. So the answer would just be x = 8?

anonymous · Answer

yea

anonymous · Answer

no such thing as imaginary time

anonymous · Answer

Thank you so much! and for explaining it!

anonymous · Answer

no prob