$\dfrac{x}{2}=\dfrac{y}{5}=k$
$\Rightarrow x=2k; y=5k$
Ta có $xy=10$
$\Rightarrow 2k.5k=10$
$\Leftrightarrow k^2=1$
$\Leftrightarrow k=\pm 1$
$k=1\Rightarrow x=2; y=5$
$k=-1\Rightarrow x=-2; y=-5$
Vậy $(x;y)=(\pm 2;\pm 5)$
x/2=y/5 <=> x/2.x/2 = y/5.x/2
= x^2/4 = x.y/10 <=> x^2/4 = 10/10 = 1
=> x^2/4 =1 => x^2 = 1.4 = 4 => x = 2 hoặc -2
=> y = 10 : 2 = 5
10 : (-2) = -5
Vậy x = 2 hoặc -2
y = 5 hoặc -5
11.Volunteers can do general.....................such as clean-up project or home repair. A. activitiesB. thingsC. labourD. jobs 12.My brother and I...................a white tiger already. A. have seenB. has seenC. seeD. are seeing 13.I................blood twice, and.....................presents to sick children in the hospital recently. A. donate -giveB. donated -gaveC. have donated -have givenD. have donated -gave 14.Volunteering is special.................me because I can help others. A. atB. forC. withD. to 15.How many novels....................Charles Dickens.........................? A. did -writeB. have -writtenC. did -writtenD. does -write 16.We......................to Ha Noi several times, but last summer weby train. A. flew-wentB. has flown –wentC. have flown -have goneD. have flown -went 17.She.................blood twenty times so far. A. donatesB. has donatedC. is donatingD. to donate 18.He...............lectures to foreign tourists about traditional food and games recently. A. givesB. gaveC. have givenD. has given 19.They have decided to clean up the neighbourhood......................it is full of rubbish. A. soB. butC. althoughD. because 20.“Have you ever..........................to Sa Pa? A. arrivedB. beenC. seenD. visited
Cho a,b,c>0 thỏa mãn a+b+c=3 CMR a^3+b^3+c^3>= a^2+b^2+c^2
What do you do to keep fit and stay healthy ? (80 words)
Trả lời câu hỏi trong hình và trả lời các tính chất hóa học của axit bazơ ,muối và phi kim là gì ?
đề bài của pic 1 +2 : Read the notice and the note from Shelia. Complete andy's note. For questions 16-20, write the information *ko cần làm bài D2
(3.4.2 mũ 16):(11.2 mũ 13.4 mũ 11-16 mũ 9)
Làm giúp mk bài trong hình vs. Mk đang cần gấp.
lập phương trình hóa học cho các phản ứng sau Mg + HCl->MgCl2 + H2 Fe2O3 + CO -> Fe + CO2 Al + H2SO4 ->Al2(SO4)3 + H2 Fe(OH)3 + H2SO4 ----> Fe2(SO4)3 + H2O
Giải hộ mình với ạ Mình cảm ơn
1.He ate a lot of fried food so he..............fat quickly A. getB. gotC. getsD. will get 2.The Japanese eat a lot offish and healthy food,................they live for a long time. A. soB. becauseC. orD. but 3.Lan.............English for more than a year but she can speak it very well. A. learnsB. learnC. learnedD. has learned 4.You should watch less TV because looking at screens in a long time..................your eyes. A. hurtB. hurtsC. is hurtingD. to hurt 5.Go Green.....................people to recycle rubbish, such as glass, cans and paper. A. to encourageB. encourageC. encouragedD. has encouraged 6.Be a Buddy has.......................education for street children. A. givenB. spentC. providedD. helped 7.He....................books for poor children for years A. has collectedB. collectsC. is collectingD. collected 8.Linh often listens to music____her parents don’t like loud noise. A. soB. butC. becauseD. and 9.Ngoc loves................outdoors with trees and flowers. A. to beB. beC. beingD. A & C 10.I think 10 years from now more people...............going to work by bicycle. A. to enjoyB. will enjoyC. enjoyingD. enjoy
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