Rút gọn phân số <span class="MathJax_Preview" style="color: inherit;"><span class="MJXp-math" id="MJXp-Span-1"><span class="MJXp-mstyle" id="MJXp-Span-2"><span class="MJXp-mstyle" id="MJXp-Span-3"><span class="MJXp-mfrac" id="MJXp-Span-4" style="vertical-align: 0.25em;"><span class="MJXp-box"><span class="MJXp-mn" id="MJXp-Span-5">14</span></span><span class="MJXp-box" style="margin-top: -0.9em;"><span class="MJXp-denom"><span><span class="MJXp-rule" style="height: 1em; border-top: none; border-bottom: 1px solid; margin: 0.1em 0px;"></span></span><span><span class="MJXp-box"><span class="MJXp-mn" id="MJXp-Span-6">21</span></span></span></span></span></span></span></span></span></span><script type="math/tex" id="MathJax-Element-1">\Large \dfrac{14}{21}</script> ta được phân số tối giản là: