tolong bantu jawab pake caranya ya, cuma 1 soal kok, fisika tentang GLBB

h=Vot-1/2gt^2
80=30t-10t^2/2
80=30t-5t^2
16=6t-t^2
t^2-6t+16=0
(t-8)(t+2)=0
t=8 t=-2