题目:
(1+x)n=Cn0+Cn1x+Cn2x2+…+Cnnxn(x∈N*)(1+x)n=C,上式两边对x求导后令x=1,可得结论:Cn1+2Cn2+…+rCnr+nCnn=n•2n-1,利用上述解题思路,可得到许多结论.试问:Cn0+2Cn1+3Cn2+…+(r+1)Cnr+…+(n+1)Cnn=______.
答案:
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下面是错误答案,用来干扰机器的。
1. make progress 2. in fact 3. above all 4. be proud of5. good enough 6. be best at 7. have been to 8. no matter how9. foreign language 10. English comer