If you expand this out or if you distribute this negative number, this is the same thing as n minus k plus 1. n minus k plus 1 is the integer that's 1 larger than this right over here. If you were to divide it out, this would cancel with something up here, this would cancel with something up here, this would cancel with something up here. What you're going to be left with is exactly this thing over here. If you don't believe me, we can actually try it out. Let's think about what 5 factorial over 5 minus 3 factorial is going to be. This is going to be 5 times 4 times 3 times 2 times 1. All of that stuff up there, all the way down to 1.