Cho số phức z thỏa mãn <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-mo" id="MJXp-Span-3" style="margin-left: 0em; margin-right: 0em;">(</span><span class="MJXp-mn" id="MJXp-Span-4">1</span><span class="MJXp-mo" id="MJXp-Span-5" style="margin-left: 0.267em; margin-right: 0.267em;">+</span><span class="MJXp-mn" id="MJXp-Span-6">2</span><span class="MJXp-mi MJXp-italic" id="MJXp-Span-7">i</span><span class="MJXp-mo" id="MJXp-Span-8" style="margin-left: 0em; margin-right: 0em;">)</span><span class="MJXp-mrow" id="MJXp-Span-9"><span class="MJXp-mo" id="MJXp-Span-10" style="margin-left: 0.167em; margin-right: 0.167em;">|</span></span><span class="MJXp-mi MJXp-italic" id="MJXp-Span-11">z</span><span class="MJXp-mrow" id="MJXp-Span-12"><span class="MJXp-mo" id="MJXp-Span-13" style="margin-left: 0.167em; margin-right: 0.167em;">|</span></span><span class="MJXp-mo" id="MJXp-Span-14" style="margin-left: 0.333em; margin-right: 0.333em;">=</span><span class="MJXp-mstyle" id="MJXp-Span-15"><span class="MJXp-mfrac" id="MJXp-Span-16" style="vertical-align: 0.25em;"><span class="MJXp-box"><span class="MJXp-msqrt" id="MJXp-Span-17"><span class="MJXp-surd"><span style="font-size: 134%; margin-top: 0.104em;">√</span></span><span class="MJXp-root"><span class="MJXp-rule" style="border-top: 0.08em solid;"></span><span class="MJXp-box"><span class="MJXp-mn" id="MJXp-Span-18">10</span></span></span></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-mi MJXp-italic" id="MJXp-Span-19">z</span></span></span></span></span></span></span><span class="MJXp-mo" id="MJXp-Span-20" style="margin-left: 0.267em; margin-right: 0.267em;">−</span><span class="MJXp-mn" id="MJXp-Span-21">2</span><span class="MJXp-mo" id="MJXp-Span-22" style="margin-left: 0.267em; margin-right: 0.267em;">+</span><span class="MJXp-mi MJXp-italic" id="MJXp-Span-23">i</span></span></span></span><script type="math/tex" id="MathJax-Element-1">\large (1+2i)|z|=\dfrac{\sqrt{10}}{z}-2+i</script>. Kh

Cho số phức z thỏa mãn (1+2i)|z|=10z2+i. Kh

4/5

Tác giả: Thầy Tùng

Đăng ngày: 18 Aug 2022

Lưu về Facebook:

Câu hỏi:

Cho số phức z thỏa mãn (1+2i)|z|=10z2+i. Khẳng định nào sau đây là đúng?

Đáp án án đúng là: D

Lời giải chi tiết:

Ta có: (1+2i)|z|=10z2+i[|z|+2+(2|z|1)i].z=10

Lấy mô đun 2 vế ta được: (|z|+2)2+(2|z|1)2.|z|=105|z|4+5|z|210=0 [|z|2=1 (tm)|z|2=2 (kt/m) 

|z|=1

Vậy |z|[12;32]