53 Are there 800 pupils in you school?

53 There are 6 children in your family

55 How much do a cack and an orange cost?

57 How much does a bottle of cooking oil cost

59 My father is going to Ha Noi by car 

60 Nam's father has a white car

61 How much beef would you like

63 I go to school by bicycle everyday

65 Phong's sister is nhung

67 Trung is Mr Minh's son

68 Huyen goes to school on foot...

69Nam is Phuong's brother

I'm going to visit Mui Ne this summer.

I'm going to visit Mui Ne this summer

help j?/

ảnh bị lỗi nhé

c.

ĐKXĐ: \(sinx\ne0\Rightarrow x\ne k\pi\)

\(1-\dfrac{\sqrt{3}cosx}{sinx}-4cosx=0\)

\(\Rightarrow sinx-\sqrt{3}cosx-4sinx.cosx=0\)

\(\Leftrightarrow sinx-\sqrt{3}cosx=2sin2x\)

\(\Leftrightarrow\dfrac{1}{2}sinx-\dfrac{\sqrt{3}}{2}cosx=sin2x\)

\(\Leftrightarrow sin2x=sin\left(x-\dfrac{\pi}{3}\right)\)

\(\Leftrightarrow\left[{}\begin{matrix}2x=x-\dfrac{\pi}{3}+k2\pi\\2x=\dfrac{4\pi}{3}-x+k2\pi\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{\pi}{3}+k2\pi\\x=\dfrac{4\pi}{9}+\dfrac{k2\pi}{3}\end{matrix}\right.\)

a.

\(\Leftrightarrow3sin3x-4sin^34x-\sqrt{3}cos9x=2sin2x\)

\(\Leftrightarrow sin9x-\sqrt{3}cos9x=2sin2x\)

\(\Leftrightarrow\dfrac{1}{2}sin9x-\dfrac{\sqrt{3}}{2}cos9x=sin2x\)

\(\Leftrightarrow sin\left(9x-\dfrac{\pi}{3}\right)=sin2x\)

\(\Leftrightarrow\left[{}\begin{matrix}9x-\dfrac{\pi}{3}=2x+k2\pi\\9x-\dfrac{\pi}{3}=\pi-2x+k2\pi\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{\pi}{21}+\dfrac{k2\pi}{7}\\x=\dfrac{4\pi}{33}+\dfrac{k2\pi}{11}\end{matrix}\right.\)

b.

\(\Leftrightarrow\sqrt{3}cosx+sin3x-sinx-sin3x=\sqrt{2}\)

\(\Leftrightarrow\sqrt{3}cosx-sinx=\sqrt{2}\)

\(\Leftrightarrow\dfrac{\sqrt{3}}{2}cosx-\dfrac{1}{2}sinx=\dfrac{\sqrt{2}}{2}\)

\(\Leftrightarrow cos\left(x+\dfrac{\pi}{6}\right)=cos\left(\dfrac{\pi}{4}\right)\)

\(\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{\pi}{6}=\dfrac{\pi}{4}+k2\pi\\x+\dfrac{\pi}{6}=-\dfrac{\pi}{4}+k2\pi\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{\pi}{12}+k2\pi\\x=-\dfrac{5\pi}{12}+k2\pi\end{matrix}\right.\)

Help mik đi mik tick cho

\(\dfrac{2}{7}=\dfrac{10}{35}=\dfrac{12}{42}=\dfrac{16}{56}\)

2/7=10/35=12/42=16/56

đề :)?

2.A

3.A