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nguyendinhquoctuan2001
2 năm trước
Cho biểu thức A= ( -a + b - c ) - ( -a - b - c ) a) Rút gọn A b) Tính giá trị của A khi a = -1 ; b=1 ; c = -2 Giúp mình nha
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giúp mình mấy câu này với 1.We cannot _______our polluted rivers and seas overnight. A. clean up B. take up C. look up D. get up 2.Trees, grasses, and other plant life play an important part in the natural ________of water. A. consequence B. elimination C. imprision D. circulation 3. What should we do to reduce the level of environmental________? A. pollute B. polluting C. pollutes D. pollution 4.The earth is being __________ and the future looks bad . A.threatened B. threat C. threatening D. threaten 5.Trees, grasses, and other plant life play an important part in the natural circulation and help ____of water. A. conservatory B. conserve C. conservation Dconservationist 6.Many animals are __________ for their fur (lông) or other valuable parts of their bodies. A.dying B. killing C. killed D. died 7. Wildlife all over the world is in __________ A.death B. danger C. threat D. risk 8. John is famous for his programmer of breading __________ A.dangerous B. dangered C. endangered D. dangerously 9.We can stop the disappearance _____plants and animals. A. of B. on C. in D. of 10.Hydroelectric dams in Vietnam have provided power __________ millions of homes and businesses. A.with B. to C. of D. for 11.Many plants and animals can be used as medicine __________ cancer, AIDS and other sicknesses. A.against B. by C. with D. for 12.The __________of forest is destroying the earth's plants and animals. A.lost B. lose C. loose D. loss 13.Trees, grasses, and other plant life play an _______part in the natural circulation of water. A. importation B. importunately C. important D. importantly 14.Without plants, most water would __________ as soon as it falls. A.run by B. run after C. run away D. run off 15. The loss of much forest is destroying Earth’s plant and animal__________ A. variousness B. variously C. various D. variety 16. __________rivers and seas can’t be cleaned up overnight. A. Beautiful B. Polluted C. Natural D. Endangered 17. Trees, grasses and other plant life __________an important part in the natural circulation of water. A. give B. take C. play D. bring 18. Many mistakes__________made by Tom. A. has been just B. have just been C. is just D. to be just 19.Trees, grasses, and other plant life _____an important part in the natural circulation of water. A. run B. play C. take D. treat 20. The fire _______the whole village in 1890. A. destroyed B. destruction C. destructive D. destroying 21.Water __________ most of the earth's surface. A.is covering B. being covered C. covers D. is covered 22.The situation is serious. Something __________ before it's too late. A.must be doing B. must do C. must have done D. must be done 23.Without plants, most water would run off as soon as it falls, taking away __________ soil. A.value B.valueless C. valuelessness D. valuable 24.“Look! This sweater is beautiful.” “____________________?” A. Why not trying it on B. Why not try on it C. Why not try it on D. Why not trying on it 25.We can't clean up our __________ rivers and seas overnight. A.polluting B. pollute C. pollution D. polluted 26.Without plants, most water would run off as soon as it falls, taking _____valuable soil. A. away B. up C. on D. in

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