JEE Math Practice Question
If $${}^n{C_r}$$ denotes the number of combination of n things taken r at a time, then the expression $$\,{}^n{C_{r + 1}} + {}^n{C_{r - 1}} + 2\, \times \,{}^n{C_r}$$ equals
- A.$$\,{}^{n + 1}{C_{r + 1}}$$
- B.$${}^{n + 2}{C_r}$$
- C.$${}^{n + 2}{C_{r + 1}}$$
- D.$$\,{}^{n + 1}{C_r}$$
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