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Prove that "^n Cr+^(n-1)Cr+...+^r Cr=^(n...

Prove that `"^n C_r+^(n-1)C_r+...+^r C_r=^(n+1)C_(r+1)` .

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CENGAGE ENGLISH-PERMUTATIONS AND COMBINATIONS-All Questions
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  3. Prove that "^n Cr+^(n-1)Cr+...+^r Cr=^(n+1)C(r+1) .

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