习题五(D 1.证明 H! x1+…+x ∑ k k1+…+km=n k1…k 2证明:对于自然数n>0, 2 1<(13…(2n-) 4n(24…(2n) 2n+1 3.证明 a+ a max(a, b 2 a+b a min(a b 210 习题五 (I) • 1. 证明: • 2. 证明: 对于自然数n>0, • 3. 证明: ( )  + + = + + = k k n k m k m n m m m x x k k n x x     1 1 1 1 1 ! ! ! 2 1 1 2 4 (2 ) 1 3 (2 1) 4 1 2 +            -  n n n n   ( ) ( ) 2 2 min , 2 2 max , a b a b a b a b a b a b - - + = - + + =