How to solve ?

Question

The height of a projectile shot up into the air is given by the formula h=16t² +128t. Find the time required for the projectile to return to its starting point.

Answer 1

The term for the height can easily be factored: h=t(16t+128)

 

When the projectile has returned to its starting point the height equals 0:

h=t*(16t+128)=0

 

This product equals 0 if either of the two factors t or (16t+128) equals 0 -> two solutions

 

solution 1: t=0 (at the start, but not the wanted solution)

solution 2: 16t+128=0 -> just solve for t and you are done!

 

Hope this helps!