证()x(x-xk =|(xd6(x-x) f(x6(x-x6)120-/(x)6(x-x6)x f"(x0)f x x x dx ò ¥ -¥ :(1) ( ) '( - ) 0 证 d '( ) ( ) ( ) | '( ) ( ) ( ) ( ) 0 0 0 0 f x f x x x f x x x dx f x d x x = - = - - - = - ò ò ¥ -¥ ¥ -¥ ¥ -¥ d d d