例1.线性空间R[x]中，线性变换D(f(x)= f'(x)J((x)=J, f(t)dt(DJ)(f(x)= D(J, (t)dt)= (x), 即 DJ = E.而,(JD)(F(x))= J(f'(x)= f f(t)dt = f(x)- f(0).. DJ ± JD.67.2线性变换的运算区区§7.2 线性变换的运算 例1. 线性空间 R x[ ] 中，线性变换 D f x f x ( ( )) = ( ) ( )( ( )) ( ( ) ) ( ) 0 , x DJ f x D f t dt f x = =  ( )( ( )) ( ( )) ( ) ( ) ( ) 0 0 x JD f x J f x f t dt f x f = = = −    而，   DJ JD. ( ( )) ( ) 0 x J f x f t dt =  即 DJ E =