binomial theorem

prove that
1*2* nCr-- 2*3* nCr-2 + 3*4*nCr-2-.............+(-1)^r(r+1)(r+2) =
2* n-3Cr

2 Answers

cant understand the question...........can u plz use latex.....

1*2*ⁿC_r- 2*3* ⁿC_r-1 + 3*4*ⁿC_r-2-.............+(-1)^r(r+1)(r+2) =
2*^n-3C_r

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