定义了一种新的K-泛函:K(f,t)∞^n=infg∈C2[0,1]{‖f-g‖∞^n+t‖δ^2ng″‖∞^n+t‖g′‖∞^n},其中‖f‖∞^n=supx∈[0,1]|δn^-β(x)f(x)|,0≤β≤2,δn^2(x)=φ^2(x)+1/n,φ(x)=x(1-x).利用此K-泛函给出了Bernstein-Kantorovich算子点态逼近的强逆不等式,即若f∈C[0,1],β=α(1-λ),0〈α≤2,0≤λ≤1,则A↓x∈[0,1],及A↓h∈(0,1/4),都存在正整数n及m满足|△↓^2hφ^λf(x)|≤Ch^αn^α/2{‖Knf-f‖∞^n+‖Kmnf-f‖∞^n}.
A new kind of K-functional:K(f,t)∞^n=infg∈C2[0,1]{‖f-g‖∞^n+t‖δ^2ng″‖∞^n+t‖g′‖∞^n},is defined,where‖f‖∞^n=supx∈[0,1]|δn^-β(x)f(x)|,0≤β≤2,δn^2(x)=φ^2(x)+1/n,φ(x)=x(1-x).with the help of K(f,t)∞^n,the strong converse inequality on pointwise approximation by Bernstein-Kantorovich operators. Let f∈C[0,1],β=α(1-λ),0〈α≤2,0≤λ≤1,then A↓x∈[0,1],and A↓h∈(0,1/4),there exist two positive integers n and m satisfying |△↓^2hφ^λf(x)|≤Ch^αn^α/2{‖Knf-f‖∞^n+‖Kmnf-f‖∞^n}.