Question 80324
the object hits the ground when the height s equals zero ... so set s=0 and solve for t


{{{-16t^2+176t+112=0}}} .. dividing by -16 gives {{{t^2-11t-7=0}}} .. no integer factors


using quadratic equation {{{t=(11 +- sqrt((-11)^2-4*1*(-7)))/(2*1)}}} so {{{t=(11 +- sqrt(149))/2}}} ... t=-.6 and t=11.6 , negative value is not realistic