cho hàm số f(x) xác định với mọi x và thỏa mãn f(x)+2f(1/x)=x^2. Tính f(1/3)

V . Supply the correct form of the verbs

1 . Please keep silent whe I ( study ).......... . It ( be ) .......... so noisy

2 . Sorry ! At this moment I ( learn ).......... in the class. I ( call) ..... you later

3 . We should not ( make ) ..... noise in the class while the teacher ( explain ) ..... the lesson

4 . Hello ! I ( help ) ........ my mother with the cooking now. What you (do )........ there

5 . I never ( watch )....... TV while you ( do ) ..... the homework

6 . What you (do) ..........here in the class at recess while all your friends (play)......... in the school yard.

7 . He often ( sit ) ....... and (watch ) ..... around while other people ( be ) busy with their work.

8 . Linda ( forget ) ........ to bring her guitar yesterday. I ( be ) ........ sure she ( forget )...........about it tomorrow, too.

9 . You ( look )...... for my sister ? She ( not be )......... at home now.

10. I ( tell ) ....... him the news when he ( come )........ .

11. Who often (help ) ....... you correct your exercises ? Both my sister and my sister ( do ) .....

12. Mary (brush ) ...... her teeth before she ( go ) .... to ed last night ?

14. They (bring )..... us some magazines if they (come )........ .