一阶导数近似 fx)=Et)fx) k=0 6(x)= 2x-(x1+X2) f,)26-3x)+4f)-f,】 22 1 ()=- 2x-(x+x2) f'(x1)≈[-f(x)+f(x2〗 h2 2h 2x-(x+1) f')*2h/,)-4fx)+3fx,J 5(x)= 2h2 二阶导数近似 6(x)=F 2 (x)=- 1 12(x)= h2 "(x)≈fxn)-2f)+fx2) h 88 0 2 1 h l(x) 1 2 2 h l(x) 2 2 1 h l(x) ( ) [ ( ) ( ) ( )] ( ) [ ( ) ( )] ( ) [ ( ) ( ) ( )] 2 0 1 2 1 0 2 0 0 1 2 4 3 2 1 2 1 3 4 2 1 f x f x f x h f x f x f x h f x f x f x f x h f x 2 0 2 1 2 h f x f x f x f x ( ) ( ) ( ) ( ) 2 1 2 0 2 2 h x x x l x ( ) ( ) 2 0 1 2 2 2 h x x x l x ( ) ( ) 2 0 2 1 2 h x x x l x ( ) ( ) 2 0 ( ) ( ) ( ) k j k j xk f x l x f 一阶导数近似 二阶导数近似