\(\frac{a}{k}=\frac{x}{a}\Rightarrow a^2=k.x\)

\(\frac{b}{k}=\frac{y}{b}\Rightarrow b^2=k.y\)

\(=\frac{a^2}{b^2}=\frac{k.x}{k.y}=\frac{x}{y}\text{ Vậy }\frac{a^2}{b^2}=\frac{x}{y}\)

1. Why don't we go fishing?

> What about going fishing ?

2. She likes to play the guitar.

> She enjoys playing the gutar

3. My car is cheaper than Mrs.Smith's car

> Mrs.Smith's car is more expensive than my car

4. Where does she live?

> What is her address?

5. John is taller than any students his class

> John is the most tallest student in his class

6. When is your birthday?

>What is your day of birth?