Cho `\Delta ABC` nhọn. CMR: `\sum cos A\le 3/2`

CHO số a =2^13 . 5^7 . Tìm số các chữ số của số a

Câu1:my father (go) to work by bus yesterday Câu2:she (have) two sisters but she (not haver ) any brothers Câu3: so far , I (leant)english for years Câu:4 We (not meet) have borther five years Câu5:It (rain) heavily for two hours Câu6: any siste often (do) aerobic everyday monning Câu7: he (not see) his foron-teacher yet Câu 6 hình như sai mn sửa hộ mik nha

Cho đoạn thẳng `AB`, `M\in AB` tm `MA^2-MB^2=a` (hằng số). Tìm quỹ tích `M`

chứng minh rằng tổng bình phương của 2 số lẻ liên tiếp không thể là số chính phương

Tính đa dạng sinh học cao thể hiện ở A. Sự phân bố sinh vật B. Sự phát triển của sinh vật C. Diện tích rừng lớn D. Nguồn gen quý hiếm

Giải thích và chọn đáp án giúp em với

READING Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions from 1 to 10. Plants and animals will find it difficult to escape from or adjust to the effect of global warming. Scientists have already observed shifts in the life cycles of many plants and animals, such as flowers blooming earlier and birds hatching earlier in the spring. Many species have begun shifting where they live or their annual migration patterns due to warmer temperatures. With further warming, animals will tend to migrate toward the poles and up mountain sides toward higher elevations. Plants will also attempt to shift their ranges, seeking new areas as old habitats grow too warm. In many places, however, human development will prevent these shifts. Species that find cities or farmland blocking their way north or south may become extinct. Species living in unique ecosystems, such as those found in polar and mountaintop regions, are especially at risk because migration to new habitats is not possible. For example, polar bears and marine mammals in the Arctic are already threatened by dwindling sea ice but have nowhere farther to go. Projecting species extinction due to global warming is extremely difficult. Some scientists have estimated that 20 to 50 percent of species could be committed to extinction with 2 to 3 Celsius degrees of further warming. The rate of warming, not just the magnitude, is extremely important for plants and animals. Some species and even entire ecosystems, such as certain types of forest, may not be able to adjust quickly enough and may disappear. Ocean ecosystems, especially fragile ones like coral reefs, will also be affected by global warming. Warmer ocean temperatures can cause coral to “bleach”, a state which if prolonged will lead to the death of the coral. Scientists estimate that even 1 Celsius degree of additional warming could lead to widespread bleaching and death of coral reefs around the world. Also increasing carbon dioxide in the atmosphere enters the ocean and increases the acidity of ocean waters. This acidification furter stresses ocean ecosystems. Question 1: Scientists have observed that warmer temperatures in the spring cause flowers to___ die instantly B. bloom earlier C, become lighter D. lose color Question 2: According to paragraph 2, when their habitats grow warmer, animali tend to move___ A.south – eastwards and down mountainsides toward lower B.north – westwards and up mountain sides toward higher C.toward the North Pole and down mountainsides toward lower D.toward the poles and up mountain sides toward higher Question 3: The pronoun “those” in paragraph 2 refers to ___ A.species B. ecosystems C. habitats D. areas Question 4: The phrase “dwindling sea ice” in paragraph 2 refers to ___ . A.the frozen water in the Artie. B.the violent Arctic Ocean. C.the melting ice in the Arctic. D.the cold ice in the Arctic. Question 5: It is mentioned in the passage that if the global temperature rose by 2 or 3 Celsius degrees___. A.half of the earth’s surface would be B.the sea level would rise by 20 C.water supply would decrease by 50 D.20 to 50 percent of species could become Question 6: According to the passage, if some species are not able to adjust quickly to warmer temperatures, ___ they may be endangered B.they can begin to develop C. they will certainly need water. D.they move to tropical forests. Question 7: The word “fragile” in paragraph 4 most probably means ___. A.very large B.easily damaged C.rather strong D. pretty hard Question 8: The bleaching of coral reefs as mentioned in paragraph 4 indicates. the water absorption of coral reefs. B.the quick growth of marine mammals. the blooming phase of sea weeds. D.the slow death of coral reefs. Question 9: The level of acidity in the ocean has increased by ___. A.the rising amount of carbon dioxide entering the B.the decrease of acidity of the pole C.the extinction of species in coastal D.the loss of acidity in the atmosphere around the Question 10: What does the passage mainly discuss? A.Influence of climate changes on human B.Effects of global warming on animals and C.Global warming and possible solutions D.Global warming and species giúp e với

Câu 12: Khi các thiết bị điện của lớp mình có dấu hiệu hư hỏng các em cần làm gì ? * 1 điểm A. Báo với cô giáo chủ nhiệm để cô giáo chủ nhiệm báo với BGH nhà trường có biện pháp sửa chữa. B. Không quan tâm, mặc kệ. Câu 13: Để đảm bảo an toàn khi sử dụng điện các em cần làm gì? * 1 điểm A. Không tắt các thiết bị điện khi tay, chân bị ướt. B. Đi dép để cách khi tắt các thiết bị điện. C. Không tự ý nghịch các thiết bị điện. D. Tất cả các ý trên Câu 14: Nhìn thấy cây cam nhà mình rất nhiều quả mà bạn Lan lại rất thèm ăn. Nếu em là bạn Lan em sẽ làm gì? * 1 điểm A. Trèo ngay lên cây và hái quả cho thỏa cơn khát của mình. B. Rủ bạn khác cùng trèo lên cây hái quả xuống ăn. C. Nhờ người lớn như: Ông, bà hay bố mẹ lấy giúp cho an toàn.

Khử hoàn toàn 0,3 mol oxit FexOy bằng Al thu được 0,4 mol Al2O3 và 0,9 mol Fe tự do. Công thức của oxit sắt là