Q20 of 118 Page 18

Let r and n be positive integers such that 1 ≤ r ≤ n. Then prove the following:

Given that we need to prove


Consider L.H.S,


We know that


And also n! = n(n – 1)(n – 2)…………2.1


⇒


⇒


⇒


= R.H.S


∴ L.H.S = R.H.S, thus proved.


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