1.

What is C(n, r) + 2C(n, r – 1) + C(n, r) equal to? a. C(n + 1, r) b. C(n –1, r + 1) c. C(n, r + 1) d. C(n + 2, r) 

Answer»

Correct option d. C(n + 2, r)

Explanation:

nrC + n(r - 1)C + n(r - 2)C

= (n + 1)rC + (n + 1)(r - 1)C = (n + 2)rC



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