Cho số phức <span class="MathJax_Preview" style="color: inherit; display: none;"></span><span id="MathJax-Element-1-Frame" class="mjx-chtml MathJax_CHTML" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle mathsize="1.44em"><mi>z</mi><mo>=</mo><mn>2</mn><mo>+</mo><mi>i</mi></mstyle></math>" role="presentation" style="font-size: 127%; position: relative;"><span id="MJXc-Node-1" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-2" class="mjx-mrow"><span id="MJXc-Node-3" class="mjx-mstyle"><span id="MJXc-Node-4" class="mjx-mrow" style="font-size: 144%;"><span id="MJXc-Node-5" class="mjx-mi"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.199em; padding-bottom: 0.298em; padding-right: 0.003em;">z</span></span><span id="MJXc-Node-6" class="mjx-mo MJXc-space3"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.101em; padding-bottom: 0.298em;">=</span></span><span id="MJXc-Node-7" class="mjx-mn MJXc-space3"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">2</span></span><span id="MJXc-Node-8" class="mjx-mo MJXc-space2"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.298em; padding-bottom: 0.445em;">+</span></span><span id="MJXc-Node-9" class="mjx-mi MJXc-space2"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.445em; padding-bottom: 0.298em;">i</span></span></span></span></span></span><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle mathsize="1.44em"><mi>z</mi><mo>=</mo><mn>2</mn><mo>+</mo><mi>i</mi></mstyle></math></span></span><script type="math/tex" id="MathJax-Element-1">\Large z=2+i</script>. Tính <span class="MathJax_Preview" style="color: inherit; display: none;"></span><span id="MathJax-Element-2-Frame" class="mjx-chtml MathJax_CHTML" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle mathsize="1.44em"><mrow class="MJX-TeXAtom-ORD"><mo stretchy="false">|</mo></mrow><mi>z</mi><mrow class="MJX-TeXAtom-ORD"><mo stretchy="false">|</mo></mrow></mstyle></math>" role="presentation" style="font-size: 127%; position: relative;"><span id="MJXc-Node-10" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-11" class="mjx-mrow"><span id="MJXc-Node-12" class="mjx-mstyle"><span id="MJXc-Node-13" class="mjx-mrow" style="font-size: 144%;"><span id="MJXc-Node-14" class="mjx-texatom"><span id="MJXc-Node-15" class="mjx-mrow"><span id="MJXc-Node-16" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.445em; padding-bottom: 0.593em;">|</span></span></span></span><span id="MJXc-Node-17" class="mjx-mi"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.199em; padding-bottom: 0.298em; padding-right: 0.003em;">z</span></span><span id="MJXc-Node-18" class="mjx-texatom"><span id="MJXc-Node-19" class="mjx-mrow"><span id="MJXc-Node-20" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.445em; padding-bottom: 0.593em;">|</span></span></span></span></span></span></span></span><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle mathsize="1.44em"><mrow class="MJX-TeXAtom-ORD"><mo stretchy="false">|</mo></mrow><mi>z</mi><mrow class="MJX-TeXAtom-ORD"><mo stretchy="false">|</mo></mrow></mstyle></math></span></span><script type="math/tex" id="MathJax-Element-2">\Large |z|</script> 3 <span class="MathJax_Preview" style="color: inherit; display: none;"></span><span id="MathJax-Element-3-Frame" class="mjx-chtml MathJax_CHTML" tabindex="0" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle mathsize="1.44em"><msqrt><mn>3</mn></msqrt></mstyle></math>" role="presentation" style="font-size: 127%; position: relative;"><span id="MJXc-Node-21" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-22" class="mjx-mrow"><span id="MJXc-Node-23" class="mjx-mstyle"><span id="MJXc-Node-24" class="mjx-mrow" style="font-size: 144%;"><span id="MJXc-Node-25" class="mjx-msqrt"><span class="mjx-box" style="padding-top: 0.045em;"><span class="mjx-surd"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.495em; padding-bottom: 0.544em;">√</span></span><span class="mjx-box" style="padding-top: 0.119em; border-top: 2.2px solid;"><span id="MJXc-Node-26" class="mjx-mrow"><span id="MJXc-Node-27" class="mjx-mn"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">3</span></span></span></span></span></span></span></span></span></span><span class="MJX_Assistive_MathML" role="presentation"><math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle mathsize="1.44em"><msqrt><mn>3</mn></msqrt></mstyle></math></span></span><script type="math/tex" id="MathJax-Element-3">\Large \sqrt{3}</script> 2 $\

Cho số phức $\Large z=2+i$ . Tính $\Large |z|$ 3 $\Large \sqrt{3}$ 2 $\

4.2/5

Tác giả: Thầy Tùng

Đăng ngày: 18 Aug 2022

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Lời giải chi tiết

Câu hỏi:

Cho số phức $\Large z=2+i$ . Tính $\Large |z|$

A. 3
B. $\Large \sqrt{3}$
C. 2
D. $\Large \sqrt{5}$

Đáp án án đúng là: D

Lời giải chi tiết:

Ta có: $\Large |z|=\sqrt{2^{2}+1^{2}}=\sqrt{5}$

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