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Krampus
2 năm trước
Chứng minh các biểu thức sau > 0 vs mọi giá trị của biến : 1) x^2+xy+y^2+1 2) x^2+5y^2+2x-4xy+10y+14 3) 5x^2+10y^2-6xy-4x-2y+3
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Ex 3: Put the verbs in the brackets into present perfect 1. You ever (eat)………………………………….. Sushi? 2. She (not/come)………………………………… here for a long time. 3. I (work)……………………………..………. here for three years. 4. You ever (be)………………………………….. to New York? 5. You (not/do) …………………………..…….yor project yet. 6. I just (see)……………….……. Andrew and he says he already (do)………………. about half of the plan. 7. I just (decide)………………….….…… to start working. 8. He (be)……………………….……. at his computer for seven hours. 9. My father (not/ play)…………….………..….. any sport since last year. 10. I’d better have a shower. I (not/have)……………….………..…. one since Thursday. 11. I don’t live with my family now and we (not/see)…………………. each other for five years. 12. I just (realize)…………………….………... that there are only four weeks to the end of term. 13. How long you (know)……………………….……. each other? 14. She ( eat)……………………………………. at the Royal Hotel yet ? 15. He (live) ……………………….……….here all his life.

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