Cho số phức <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-mi MJXp-italic" id="MJXp-Span-3">z</span><span class="MJXp-mo" id="MJXp-Span-4" style="margin-left: 0.333em; margin-right: 0.333em;">=</span><span class="MJXp-mn" id="MJXp-Span-5">2</span><span class="MJXp-mo" id="MJXp-Span-6" style="margin-left: 0.267em; margin-right: 0.267em;">+</span><span class="MJXp-mn" id="MJXp-Span-7">11</span><span class="MJXp-mi MJXp-italic" id="MJXp-Span-8">i</span></span></span></span><script type="math/tex" id="MathJax-Element-1">\large z=2+11i</script>. Xác định phần thực của z . 2