证明n*(x+1)^(n-1)=Σ(k=0到n)k*c(n,k)*x^(k-1)
证明n*(x+1)^(n-1)=Σ(k=0到n)k*c(n,k)*x^(k-1)
试证明 x/[n(n+k)]=(x/k)[1/n-1/(n+k)]
证明组合C(n-1,k)+C(n-2,k)+…+C(k+1,k)+C(k,k)=C(n,k+1)
证明C(0,n)+C(1,n+1)+C(2,n+2)+...+C(k,n+k)=C(k,n+k+1)
试证明:∑(i=1到n)C(n,i)*k^(n-i)*k*i=n*k*(k+1)^(n-1)
证明C(n+1,k)=C(n,k-1)+C(n,k) 及 C(n,r)*C(r,k)=C(n,k)*C(n-k,r-k)
请问1^k+2^k+3^k+.+n^k=?
排列组合计算:(1/k!)X[1/(n-k)!]=?
求极限k^2/(n^3+k^3) n趋于无穷,k=1到n
lim x->+无穷 x/[x^n+1-(x-1)^n+1]=k,n为正整数,求n和k
不展开 用排列组合意义证明 C(n-1,k-1)C(n,k+1)C(n+1,k)=C(n-1,k)C(n,k-1)C(n
证明排列组合等式SUM:k^2*Cnk=2^(n-2)*n*(n+1) (k=1到n)