広田の方法
D x 2 f ⋅ g = f x x g − 2 f x g x + f g x x {\displaystyle D_{x}^{\,2}f\cdot g=f_{xx}g-2f_{x}g_{x}+fg_{xx}}
D x 3 f ⋅ g = f x x x g − 3 f x x g x + 3 f x g x x − f g x x x {\displaystyle D_{x}^{\,3}f\cdot g=f_{xxx}g-3f_{xx}g_{x}+3f_{x}g_{xx}-fg_{xxx}}
D x 4 f ⋅ g = f x x x x g − 4 f x x x g x + 6 f x x g x x − 4 f x g x x x + f g x x x x {\displaystyle D_{x}^{\,4}f\cdot g=f_{xxxx}g-4f_{xxx}g_{x}+6f_{xx}g_{xx}-4f_{x}g_{xxx}+fg_{xxxx}}
D x D t f ⋅ g = f t x g − f t g x − f x g t + f g t x {\displaystyle D_{x}D_{t}f\cdot g=f_{tx}g-f_{t}g_{x}-f_{x}g_{t}+fg_{tx}}