2-1 Lagrange插值(15)

固定任一 x,作辅助函数，令Ψ (t )= f (t ) L1 (t ) k ( x)(t x0 )(t x1 ),满足Ψ (xi )=0, i=1,2且Ψ (x)=0,即Ψ (t)有3个零点x0, x1和 x。 R1 ( x) k=由ψ (t )= 0 (x) ( x x0 )( x x1 )

其中R1 ( x)= f ( x) L1 ( x) R1 ( x) (t x0 )(t x1 )ψ (t )= f (t ) L1 (t ) ( x x0 )( x x1 )