Tìm chữ số a.b để: 21 x a + b chia hết cho 7

1.Cho hình thang cân ABCD(AB//CD,AB=2CD,và AB=AD+CB) a)tính các góc của hình thang b)tính các góc tạo bởi 2 đường chéo c)chứng minh rằng đường chéo AC vuông góc với cạnh bên AB 2.Cho tam giác ABC vuông tại A.kẻ đường cao AH 1 điểm M thuộc cạnh huyền BC sao cho CM=CA.Đường thẳng đi qua M và //AC cắt AB tại I a)chứng minh ACMI là hình thang vuông b)chứng minh MI=MH và AI=AH c)chứng minh AB+AC<AH+BC

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Trên cùng một nửa mặt phẳng bờ chứ tia Ox , Vẽ 2 tia Oy,Oz sao cho xOy = 30độ , xOz = 120độ , vẽ Oa là tia đối của tia Ox . Tính aOz và aOy

Giúp mình câu 4,3 với, nhớ giải chi tiết nhé

61. He remember ( drive) up to the crossroads but nothingelse after the accident. 62. Do try ( make ) less noise. I’m trying (concentrate). 63. Have you ever stopped (wonder) why she behaved like that? 64. We really need (do) some shopping, we’re running out of everything. 65. I’ve tried (jog) and aerobics but I still can’t lose weight 66. I’ll stop (lend) you money if you waste it on cigarettes. 67. I can’t get this table through the door. Have you tried ( take) off the legs? 67. The house needs (paint) soon. 68.Mary will need (make) a new dress for the party. 69. Would you like (come)to a lecture on Wagner tonight?- No, thanks. I like (listen) to music but I don’t like (listen) to people talking about it. 70. Do you feel like (dine) out or Would you rather (have) dinner at home? -I’d loke (go) out. 71. We stopped once (buy) petrol and then we stopped again(ask) someone the way. 72. When I caught them cheat me , I stopped(buy) petrol there and started ( deal) with your garage instead. 73. The lecturer began by telling us where the island was and went on ( talk) about its history. 74.I wish I hadn’t tried ( repair) it. I only made it worse. 75. I regret ( say) that I won’t be able to come to the party , but I hope you have a great time. 76. I regret ( say )that We’ve decided not to offer you the job. 77. I regret (say) that I don’t like your new boy friend. 78. He remembered (see) Jane on the way home from work. 79. She remembered ( send) her mother a birthday card. 80. He went on ( talk) about himself for hours and hours . 81. She was very angry with him for forgetting ( lock) the back door. 82. The Professor mentioned Botticelli, and went on (talk) about Renaissance. 83. I’ve tried (open) the bonnet , but it seems to be stuck. 84. Have you tried (clean) the spark plugs? 85. I’ll never forget (see) the Taj Mahal for the first. 86. I think we ought to stop (have) something to eat soon. 87. They stopped (go) out in the evening when they had their first child. 88. Your business is a complex shambles-the whole thing needs (reorganise). 89. I meant ( write) him a letter of condolence, but I never got round to it. 90. If you do join the Navy, it’ll mean(be) away from home for months on end. 91. I’ve always regretted (not learn) to play the piano at school. 92. I dread (think) what he’s going to say when he finds out I’ve crashed the car. 93. I need (have) a word in your ear. It’s about your trip to Italy nextweek. 94. The house is a wreck. If you buy it , it’ll mean (live) in chaos for months. 95. After three months without work, he regretted (leave) his safe job at the bank. 96. She dreaded (have) to see her ex-husband again in court. 97. They don’t allow (smoke) in the auditorium, they don’t want (risk) setting on fire. 98. Your hair needs (cut). 99.Please stop (ask) me such stupid questions. 100. I didn’t mean (upset) you. 101. He remembers part of her childhood quite clearly

Cho tam giác ABC vuông tại A có góc C= 60 độ. Lấy điểm D đối xứng với điểm C qua AB. a) Có nhận xét gì về tam giác DBC ? Vì sao? b) Chứng minh AC=1/2 BC ? c) Trên tia ba lấy điểm O sao cho BC=2/3 BA. Chứng minh O là tâm đường tròn ngoại tiếp tam giác DBC.

Xét tính chẵn lẻ của hàm số y=1-sin²x y=1+tanx y=x².sinx

Giúp mình vs ae ơi .Nếu đúng sẽ đánh giá 5 sao

Năm 1401 đến năm 1500 thuộc thế kỉ .....