So sánh cặp VCB sau: <span class="katex-r" data-latex="displaystyle α(x) = st3{1+6x} - st{1+4x}"></span> và <span class="katex-r" data-latex="displaystyle bη(x) = x^2"></span>, khi <span class="katex-r" data-latex="displaystyle x to 0"></span>