Question 999922
the time that it takes to reach the ground:

a)
{{{h(t)=-16t^2+64t+960}}} 
the object will reach the ground, when its height is {{{zero}}}
{{{0= -16t^2+64t+960}}} 
{{{0= -16(t^2-4t-60)}}}
{{{0= -16(t^2-10t+6t-60)}}}
{{{0 = -16 (t-10) (t+6)}}}
=>{{{t=10}}} or {{{t=-6 }}}

Only the + sign makes sense. =>{{{t=10}}}
b) 
{{{0= -16t^2 +80t+576}}} 
{{{0= -16(t^2 -5t-36 )}}}
{{{0= -16(t^2 -9t+4t-36 )}}}
{{{0= -16((t^2 -9t)+(4t-36 ))}}}
{{{0= -16(t(t -9)+4(t-9 ))}}}
{{{0 = -16 (t-9) (t+4)}}}

=>{{{t=9}}} or {{{t=-4}}}
Only the + sign makes sense. =>{{{t=9}}}


your function c) is same as a)