Question 1181972


 {{{h = -16t^2 + 34t + 15  }}}


the ball will hit the ground when {{{h=0}}}

{{{0= -16t^2 + 34t + 15  }}}....factor

{{{0= -(16t^2 -34t - 15)  }}}

{{{0= -(16t^2 +6t-40t - 15)  }}}

{{{0= -((16t^2 +6t)-(40t+15))  }}}

{{{0= -(2t(8t +3)-5(8t+3))  }}}

{{{0 = -(2t - 5) (8t + 3) }}}

solutions:

if {{{0 = -(2t - 5)  }}}=>{{{2t =5  }}}=>{{{t =2.5  }}}
if {{{0 =  8t + 3 }}}=>{{{ 8t=-3 }}}=>{{{ t=-3/8 }}}-> disregard negative time

the ball will hit the ground after {{{2.5  }}} seconds