The next step we multiply out by negative t.
And that's because we want to get rid of this t, okay? So let's do that. Negative t times this gives you this negative t times this gives you that negative t times a negative whatever gives us a positive. So plus this whole term, step seven, is basically the TS cancel out. So we get this whole thing minus these t's. Next step, what I do is I switch these guys to make it look more like the actual equation.