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Xét \(\dfrac{x}{3}=\dfrac{y}{4}=\dfrac{z}{2}=k\)

\(\Rightarrow\left\{{}\begin{matrix}x=3k\\y=4k\\z=2k\end{matrix}\right.\) (1)

Thay (1) vào \(x^2+y^2=100\)

\(\Rightarrow\)\(x^2+y^2=100\)\(=\left(3k\right)^2+\left(4k\right)^2\)

\(=9k^2+16k^2\)

\(=25k^2=100\)

\(\Rightarrow k^2=4\)

\(\Rightarrow k=\pm2\)

\(\Rightarrow\left\{{}\begin{matrix}x=\pm6\\y=\pm8\\z=\pm4\end{matrix}\right.\)

Xét \(\dfrac{x}{7}=\dfrac{4}{y}=\dfrac{z}{2}=k\)

\(\Rightarrow\left\{{}\begin{matrix}x=7k\\y=4k\\z=2k\end{matrix}\right.\) (2)

Thay (2) vào \(x-3x=-2x=9=-2.7k=9\)

\(\Rightarrow k=\dfrac{-9}{14}\)

\(\Rightarrow\left\{{}\begin{matrix}x=7k=7.\dfrac{-9}{14}=\dfrac{-9}{2}\\y=4k=4.\dfrac{-9}{14}=\dfrac{-18}{7}\\z=2k=2.\dfrac{-9}{14}=\dfrac{-9}{7}\end{matrix}\right.\)

\(\dfrac{x-1}{4}=\dfrac{2}{\left(x-1\right)^2}\)

\(\Rightarrow\left(x-1\right)^3=2.4=8\)

\(\Rightarrow x-1=2\Rightarrow x=3\)

\(x^2-2xy+y^2-4\)

\(=\left(x-y\right)^2-2^2\)

\(=\left(x-y-2\right)\left(x-y+2\right)\)

1. Where is your house ?

It is upstairs

2. Is your house big or small ?

It is small

3. How many rooms are there in your house ?

There are six rooms in my house

What are they ?

They are kitchen, three bedroooms, living room and two bathrooms

4. What room do you like best ? Why ?

It is my bedroom beacause it is very tidy and comfortable

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+ Phê phán xã hội phong kiến và Giáo hội

+ Đề cao giá trị con người