The second method is doing what i did for question two in your previous post, but at the end change C(5,1) to C(5,4) and C(6,2) to C(6,4), why can we do that?
C(n,r) = C(n, n - r)
so, for example, C(6,2) = C(6, 6 - 2) = C(6,4)
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By Pascal's Formula,
So, we have:
.........now expand the last combination using the formula
Now, wasn't that a lot nicer?!