6. They have studied English since 1990
(-) They haven't studied English since 1990
(?) Have they studied English since 1990 ?
7. The train has just left the station
(-) The train hasn't just left the station
(?) Hasn't the train just left the station ?
8. He has written to me lately
(-) He hasn't written to me lately
(?) Has he written to you lately ?
9. The child has slept for three hours
(-) The child hasn't slept for three hours
(?) Has the child slept for three hours ?
10. I have already seen that play before
(-)  I haven't already seen that play before
(?) Have you already seen that play before ?

1. I have just seen my sister in the park.
(-) I haven't seen my sister in the park.
(?) Have you seen your sister in the park ?
2. She has finished her homework recently
(-) She hasn't finished her homework recently
(?) Has she finished her homework recently ?
3. Daisy has read that novel several times
(-) Daisy hasn't read that novel several times
(?) Has Daisy read that novel several times ?
4. I have seen "Titanic" three times
(-) I haven't seen "Titanic" three times
(?) Have you seen "Titanic" three times ?
5. Mary has lived in this house for ten years
(-) Mary hasn't lived in this house for ten years
(?) Has Mary lived in this house for ten years ?

tính giá trị của các biểu thức 

a, A=x³- 30x²- 31x + 1 tại x = 31

b, B= x⁵- 15x⁴ + 16x³- 29x² + 13x tại x = 14

Giúp mik với

6² . 6⁴ - 4³( 3⁶ - 1 )

My cousin sings better than me.

1. High__Highter__The hightest

2. Small__Smaller__The smallest

3. Large__Larger__The largest

4. Heavy__Heavier__The heaviest

5. New__Newer__The newest

6. Interesting__More interesting __The most interesting

7. Beautiful__More beautiful__the most beautiful

8. difficult__more difficult__the most difficult

9. creative__more creative__the most creative

10. careful__more careful__the most careful

11. Bad__worse__ the worst

12. Many/much__more__the most

13. Good__better__the best

14. Little__less__ the least