X=ata,x,-x )=f1 P(x2)=a0+a1(x2-x)+a2(x2-x0)x2-x)=f2 o a1=x1 2-f0f1-f3 当 0 0 0 1 0 1 1 0 1 2 0 1 2 0 2 2 0 2 1 2 ( ) ( ) ( ) ( ) ( ) ( )( ) n n n P x a f P x a a x x f P x a a x x a x x x x f  = =   = + − =  = + − + − − =    0 0 1 0 1 1 0 2 0 1 0 2 0 1 0 2 2 1 a f f f a x x f f f f x x x x a x x  =  −  =  −    − − −  − −  =  −  