So we simply sum up the exponents and that gives us two. And what that means is by doubling A we double v as long as everything else remains constant. Likewise, if we double B while A and K is constant, v will also double. But if we double A and B while K is constant, we quadruple that v value. And so that's what it means for reaction to actually be 1st 2nd order. Now we can also have a slightly different second order reaction.