Để \(\frac{\sqrt{x+1}}{\sqrt{x-2}}=\sqrt{\frac{x+1}{x-2}}\) là số nguyên thì \(\frac{x+1}{x-2}\) là số chính phương

Khi đó \(x+1⋮x-2\)

\(\Leftrightarrow x-2+3⋮x-2\)

\(\Leftrightarrow3⋮x-2\)

\(\Leftrightarrow x-2\in\left\{1;3;-1;-3\right\}\)

\(\Leftrightarrow x\in\left\{4;5;1;-1\right\}\)

Thay vào thử nha !

Look and say. (6 points)

1. Hello, ________.

2. I have a ________.

3. This is ________. 

4. There's ________. 

5. Touch ________. 

\(P=\sqrt{x^2+\frac{1}{x^2}}+\sqrt{y^2+\frac{1}{y^2}}\)

\(\ge\sqrt{\left(x+y\right)^2+\left(\frac{1}{x}+\frac{1}{y}\right)^2}\) ( min cốp sờ ki )

\(\ge\sqrt{\left(x+y\right)^2+\frac{16}{\left(x+y\right)^2}}\) ( cau chy sờ goát )

\(=\sqrt{4^2+\frac{16}{4^2}}=\sqrt{17}\)

Dấu "=" xảy ra tại \(x=y=2\)

Is that true.Xem ra cách t đỡ sốc hơn cách m nếu đúng:v

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II/ Choose the best answer.

1.     Mai hates eating fast food because it’s not good ……her health.

a.      on           b. for           c. at             d. in

2.     If you want to live long, you …… eat  much red meat.

a.      should              b. needn’t    c. have to    d. shouldn’t

3.      Don’t read in bed, ................ you’ll harm your eyes.

a.      or            b. and                   c. but           d. so