Cho hàm số (C): \(y=\frac{2x-1}{x+1}\) và đường thẳng (d): y=2x-m . Tìm m để (d) cắt (C) tai 2 điểm A, B thoả mãn:
\(\frac{1}{OA}+\frac{1}{OB}=1\) ( với O là gốc toạ độ).
Giải chi tiết hộ mk <3
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\(A=\cos^215^o-\cos^225^o+\cos^235^o-\cos^245^o+\cos^255^o-\cos^265^o+\cos^275^o\)
\(A=\sin^275^o-\sin^265^o+\sin^255^o-\sin^245^o+\cos^255^o-\cos^265^o+\cos^275^o\)
\(A=\left(\sin^275^o+\cos^275^o\right)-\left(\sin^265^o+\cos^265^o\right)+\left(\sin^255^o+\cos^255^o\right)-\sin^245^o\)
\(A=1-1+1-\frac{1}{2}\)
\(A=\frac{1}{2}\)
Áp dụng BĐT AM-GM ta có:
\(ab\le\frac{\left(a+b\right)^2}{4}\le\frac{1}{4}\)
Và \(P=a^2+b^2+\frac{1}{a^2}+\frac{1}{b^2}\)
\(=a^2+\frac{1}{16a^2}+b^2+\frac{1}{16b^2}+15\left(\frac{1}{16a^2}+\frac{1}{16b^2}\right)\)
\(\ge2\sqrt{a^2\cdot\frac{1}{16a^2}}+2\sqrt{b^2\cdot\frac{1}{16b^2}}+15\cdot2\sqrt{\frac{1}{16a^2}\cdot\frac{1}{16b^2}}\)
\(=\frac{1}{2}+\frac{1}{2}+15\cdot2\cdot\frac{1}{16ab}\)\(\ge1+15\cdot2\cdot\frac{1}{16\cdot\frac{1}{4}}=\frac{17}{2}\)
Xảy ra khi \(a=b=\frac{1}{2}\)
SƯU TẦM
50 Đề thi học sinh giỏi
Anh Văn 9
Part 2:. Listen and write down the times in words. You will hear the recording three times. (9 points) 32
KỲ THI CHỌN HỌC SINH GIỎI LỚP 9 TOÀN HUYỆN 95
Năm học 2009-2010 95
MÔN: TIẾNG ANH 95
KỲ THI CHỌN HỌC SINH GIỎI LỚP 9 TOÀN HUYỆN 101
Năm học 2009-2010 101
MÔN: TIẾNG ANH 101
KỲ THI CHỌN HỌC SINH GIỎI LỚP 9 TOÀN HUYỆN 107
Năm học 2009-2010 107
MÔN: TIẾNG ANH 107
KỲ THI CHỌN HỌC SINH GIỎI LỚP 9 TOÀN HUYỆN 109
Năm học 2009-2010 109
MÔN: TIẾNG ANH 109
1. I'll ............................................................................................................................................... 138
II. READING 138
M«n tiÕng anh 142
M«n tiÕng anh 144
Question4: a) Change these sentences into passive voice 145
M«n tiÕng anh 146
Phßng Gi¸o Dôc §Ò thi chän häc sinh giái líp 9 THCS 147
Phßng Gi¸o Dôc §Ò thi chän häc sinh giái líp 9 THCS 149
Phßng Gi¸o Dôc §Ò thi chän ®éi tuyÓn häc sinh giái líp 9 THCS 150
N¨m häc 2004-2005 151
Question 8: Rewrite the following sentences, beginning each sentences with the cues 155
Question 8: Rewrite the following sentences, beginning each sentences with the cues 157
Question II: Supply the corect form of the verbs in the brackets 158
than B. with C. at D. for 158
Question II: Supply the corect form of the verbs in the brackets 160
M«n tiÕng anh 162
M«n tiÕng anh 164
M«n tiÕng anh 166
M«n tiÕng anh 168
Question 6: 172
a) Change these sentences into passive voice 172
Së Gi¸o dôc & §µo t¹o kú thi tuyÓn sinh vµo líp 10 – THPT chuyªn lam s¬n 173
Thanh ho¸ N¨m häc 2005-2006 173
Question4: a) Change these sentences into passive voice 175
Question II: Supply the corect form of the verbs in the brackets. 181
Question II: Supply the corect form of the verbs in the brackets. 182
Trêng thcs Nga Thuy 202
§Ò thi chän ®éi tuyÓn- §Ò 1 202
Häc sinh giái m«n tiÕng anh lop 9- vong 2 202
N¨m häc 2008-2009- 120 phut 202
7.If anyone succeeds in solving the problems, it will probably be him. 202
VI Use the following sets of words or phrases to write complete sentences . 204
VI 1. We haven't seen you for such a long time . 205
I. Choose the word in each group that has underlined part pronounced differently from the rest. Circile the letter you choose (5 p) 36
III. Choose the answer A,B,C or D to complete each sentence. Circle the letter you choose (10p) 36
12. The hotel room…over a very beautiful park 36
13. On Sundays in England, most shops were closed and…the theaters and cinemas 36
14. We didn’t…to the station in time to catch the train 36
15. Either John or his brothers…the money 36
16. I remember…the letter sometime ago but I can’t remember exactly when 36
17. Jane lost her case because it didn’t have…with hername on 36
18. Do you know what time the train…for Leeds? 36
19. The policeman warned us…there 36
20. The trip was very interesting. Jack wishes he…enough time to join 36
IV. Fill in the blank with the correct form of the words in capital letters (10 p) 36
V. Give the correct tense or form of the verbs in brackets to complete the following sentences (10p) 37
VI. Fill in each blank with one suitable preposition (10p) 37
VII. Fill in each numbered blank with one suitable word.(10p) 37
VIII. Read the passage carefully and choose the best answer A,B,C or D by circling the letter you choose (10 p) 37
X.Rewrite the sentences, beginning with the given words (10p) 38
Unless… 38
In case… 38
89.They are building a new museum in the city centre 38
X.Rewrite the sentences, beginning with the given words
Mk đã in cho cậu đề thi hc sinh giỏi lớp 9 rồi nhưng mk ko thể copy cả nên cậu vào link này nhé !
http://s2.vndoc.com/data/file/2013/thang12/30/50-Bo-de-thi-HSG-Anhvan-9.doc
Ok !! chi tiết =))
\(\sqrt{6+\sqrt{24}+\sqrt{12}+\sqrt{8}}-\sqrt{4+2\sqrt{3}}\)
\(=\sqrt{1+2+3+2\sqrt{2}.\sqrt{1}+2\sqrt{2}.\sqrt{3}+2\sqrt{1}.\sqrt{3}}-\sqrt{3+2\sqrt{3}+1}\)
\(=\sqrt{\left(\sqrt{1}+\sqrt{2}+\sqrt{3}\right)^2}-\sqrt{\left(\sqrt{3}+1\right)^2}\)
\(=1+\sqrt{2}+\sqrt{3}-\sqrt{3}-1\)
\(=\sqrt{2}\)