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help với ạ
help với ạ
KY
5 tháng 7 2021
use
is jane watching
doesn't go
is ating
do you study
am not listening- am playing
is raining- rains
are reading
am often playing=>often plays
is wanting=>wants
doesn't =>don't
have=>are having
skip=>skipping
is having=>has
cook =>am cooking
MN
5 tháng 7 2021
IV,
1. use
2. Is Jane watching...?
3. doesn't go
4. is eating
5. Do you sutdy...?
6. amn't listening... am playing
7. is going to rain... rains
8. are reading
V,
1. playing=> play
2. is wanting=> want
3. doesn't=> don't
4. have=> are having
5. skip=> skipping
6. is having=> has
7. cook=> am cooking
NV
Nguyễn Việt Lâm
Giáo viên
14 tháng 9 2021
c.
ĐKXĐ: \(sinx\ne0\Rightarrow x\ne k\pi\)
\(1-\dfrac{\sqrt{3}cosx}{sinx}-4cosx=0\)
\(\Rightarrow sinx-\sqrt{3}cosx-4sinx.cosx=0\)
\(\Leftrightarrow sinx-\sqrt{3}cosx=2sin2x\)
\(\Leftrightarrow\dfrac{1}{2}sinx-\dfrac{\sqrt{3}}{2}cosx=sin2x\)
\(\Leftrightarrow sin2x=sin\left(x-\dfrac{\pi}{3}\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=x-\dfrac{\pi}{3}+k2\pi\\2x=\dfrac{4\pi}{3}-x+k2\pi\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{\pi}{3}+k2\pi\\x=\dfrac{4\pi}{9}+\dfrac{k2\pi}{3}\end{matrix}\right.\)
NV
Nguyễn Việt Lâm
Giáo viên
14 tháng 9 2021
a.
\(\Leftrightarrow3sin3x-4sin^34x-\sqrt{3}cos9x=2sin2x\)
\(\Leftrightarrow sin9x-\sqrt{3}cos9x=2sin2x\)
\(\Leftrightarrow\dfrac{1}{2}sin9x-\dfrac{\sqrt{3}}{2}cos9x=sin2x\)
\(\Leftrightarrow sin\left(9x-\dfrac{\pi}{3}\right)=sin2x\)
\(\Leftrightarrow\left[{}\begin{matrix}9x-\dfrac{\pi}{3}=2x+k2\pi\\9x-\dfrac{\pi}{3}=\pi-2x+k2\pi\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{\pi}{21}+\dfrac{k2\pi}{7}\\x=\dfrac{4\pi}{33}+\dfrac{k2\pi}{11}\end{matrix}\right.\)
27 tháng 1 2022
\(\dfrac{2}{7}=\dfrac{10}{35}=\dfrac{12}{42}=\dfrac{16}{56}\)
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