Proof that ncr+2ncr-1+ncr-2=n+2cr

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In this lesson I have explained in details how to proof ncr+ncr-1+ncr-2=n+2cr using combinatorial and factorial identities.
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I think you don't know the property of Combination. This question could be solved in just 1min by using property.
nCr+nCr-1= n+1Cr.

failedgamer