Ta có : \(x^2-2x-1=x^2-2x+1-2\)\(=\left(x-1\right)^2-\left(\sqrt{2}\right)^2\)

\(=\left(x-1-\sqrt{2}\right)\left(x-1+\sqrt{2}\right)\)

Cho \(x^2-2x-1=0\)

\(\Leftrightarrow\left(x-1-\sqrt{2}\right)\left(x-1+\sqrt{2}\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-1-\sqrt{2}=0\\x-1+\sqrt{2}=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1+\sqrt{2}\\x=1-\sqrt{2}\end{matrix}\right.\)

Vậy nghiệm của đa thức là \(x=1-\sqrt{2};x=1+\sqrt{2}\)

1. waited \(\rightarrow\) were waiting.

2. went \(\rightarrow\) go

3. was \(\rightarrow\) were

4. phoned -> phone

5. Do you enjoy the party ?

6. enjoined ->enjoyed

7. are smelling-> smell

8. knewed -> knew

9. for -> since

10. since -> for

Hardly had we finished dinner when the thunderstorm broke.

D. People who are competitive are more likely to suffer from the effects of stress for their health.

1. These letters are typed by Mary in the office.

2. The cake is being cut with sharp knife by Mary.

3.I was sent a present last week.

4. Trả can't be made with cold water

5.The window was broken and some pictures was taken away by the boys.

6. Why wasn't he helped ?

7. Where is English spoken ?

8. Is a poem going to be written by her ?

9. Were you given some exercises by the teacher ?