Expand the following: $$\begin{array}{rl}{t}_s=\frac{-F{b}_2}{m}\ast t{s}_2+g\ast t{s}_2"\ast sin\alpha +v_0& =t{s}_2\ast (\frac{F{b}_2}{m}-g\ast sin\alpha )\\ & =\frac{v_0}{\frac{-F{b}_2}{m}-g\ast sin\alpha }\end{array}$$