Giúp mình câu 2b với gấp lắm ạ

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Giúp mình câu 2b với gấp lắm ạ

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Giúp mình câu 2b với gấp lắm ạ
giup-minh-cau-2b-voi-gap-lam-a

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Môn Toán King 4 years 2020-10-13T16:05:16+00:00 2020-10-13T16:05:16+00:00 2 Answers 98 views 0

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Captcha* Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )

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About King

Dau · Answer 1 · 2020-10-13T16:06:31+00:00

Đáp án:

$x = {\frac{53 π}{84}; \frac{5 π}{12}; \frac{59 π}{84}}$

Giải thích các bước giải:

$\begin{array}{l} \cos 7 x - \sqrt{3} \sin 7 x = - \sqrt{2} \\ \Leftrightarrow \frac{\sqrt{3}}{2} \sin 7 x - \frac{1}{2} \cos 7 x = \frac{\sqrt{2}}{2} \\ \Leftrightarrow \sin (7 x - \frac{π}{6}) = \sin \frac{π}{4} \\ \Leftrightarrow [\begin{matrix} 7 x - \frac{π}{6} = \frac{π}{4} + k 2 π \\ 7 x - \frac{π}{6} = \frac{3 π}{4} + k 2 π \end{matrix} \\ \Leftrightarrow [\begin{matrix} 7 x = \frac{5 π}{12} + k 2 π \\ 7 x = \frac{11 π}{12} + k 2 π \end{matrix} \\ \Leftrightarrow [\begin{matrix} x = \frac{5 π}{84} + k \frac{2 π}{7} \\ x = \frac{11 π}{84} + k \frac{2 π}{7} \end{matrix} (k \in Z) \\ T a c ó : \\ \frac{2 π}{5} < x < \frac{6 π}{7} \\ \Leftrightarrow [\begin{matrix} \frac{2 π}{5} < \frac{5 π}{84} + k \frac{2 π}{7} < \frac{6 π}{7} \\ \frac{2 π}{5} < \frac{11 π}{84} + k \frac{2 π}{7} < \frac{6 π}{7} \end{matrix} \\ \Leftrightarrow [\begin{matrix} \frac{143}{120} < k < \frac{67}{24} \\ \frac{113}{120} < k < \frac{61}{24} \end{matrix} \\ \Rightarrow [\begin{matrix} k = 2 \\ k = {1; 2} \end{matrix} (k \in Z) \\ \Rightarrow [\begin{matrix} x = \frac{29 π}{84} \\ x = \frac{5 π}{12} \\ x = \frac{59 π}{84} \end{matrix} \\ V ậ y x = {\frac{53 π}{84}; \frac{5 π}{12}; \frac{59 π}{84}} \end{array}$

Philomena · Answer 2 · 2020-10-13T16:07:02+00:00

Philomena

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2020-10-13T16:07:02+00:00 October 13, 2020 at 4:07 pm

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