`(30)/(x+y)+(20)/(x-y)=(10)/y`
`⇔(30(x-y))/((x-y)(x+y))+(20(x+y))/((x-y)(x+y))=(10)/y`
`⇔(30x-30y+20x+20y)/((x-y)(x+y))=(10)/y`
`⇔(50x-10y).y=10(x-y)(x+y)` (nhân chéo)
`⇔50xy-10y²=10x²-10y²`
`⇔50xy=10x²`
`⇔5y=10x²:10x`
`⇔5y=x`
Đáp án:
$\displaystyle 5y=x$
Giải thích các bước giải:
$\displaystyle \begin{array}{{>{\displaystyle}l}} \frac{30}{x+y} +\frac{20}{x-y} =\frac{10}{y}\\ \Leftrightarrow \frac{30( x-y)}{( x-y)( x+y)} +\frac{20( x+y)}{( x-y)( x+y)} =\frac{10}{y}\\ \Leftrightarrow \frac{30x-30y+20x+20y}{( x-y)( x+y)} =\frac{10}{y}\\ \Leftrightarrow ( 50x-10y) .y=10( x-y)( x+y)\\ \Leftrightarrow 50xy-10y^{2} =10x^{2} -10y^{2}\\ \Leftrightarrow 50xy=10x^{2}\\ \Leftrightarrow 5y=x\\ Vậy\ 5y=x \end{array}$
Cho ∆ABC vuông cân tại A. Gọi M là 1 điểm thuộc cạnh BC, kẻ MD ⊥ AB tại D, ME ⊥ AC tại E. Gọi I là trung điểm của BC. ∆IDE là tam giác gì? Giúp mình với hứa vote 5*
II. Complete the following sentences with the correct form of the verbs in brackets. (5 pts) a. I’m sorry I (1. not be) _____ in when you came round. I would like (2. see) _____ you .b. It was our fault to keep Jane (3. wait) _____ so long. We (4. inform) _____ her in advance.c. The number of students (5. attend) _____ English courses (6. probably reduce) _____ next year.d. I'm sorry; we seem (7. run) _____ out of coffee. We (8. have) _____ some tea instead? e. Just relax, Anthony. As soon as your sprained ankle (9. heal) _____, you can play soccer again. At this time nextweek, you (10. play) _____ soccer again III. Supply the correct form of the words in brackets. (10pts) Most of us want to be healthy all our lives. Doctors say that to achieve this, (1. prevent) _____ is better thancure, so they advise us to avoid certain (2. active) _____ like smoking, (3. excess) _____ drinking or taking certainsubstances such as drugs, to eat (4. sense) _____, to take plenty of regular and demanding exercise, and, ofcourse, to live in clean, hygienic conditions.(5. Fortunate) _____, many of us have difficulty following this very good advice. Exercise, for example, can beboring, time-consuming and (6. convenience) _____. Even worse, some of our favorite foods like beef - burgers,(7. can) _____ drinks, ice-creams and crisps are the (8. health) _____ ones, and some things that young peopleoften really enjoy, like bungee jumping, car racing and (9. parachute) _____ are among the most (10. excite) _____things we can do, though, of course, they can be dangerous. What's better, live now and pay later or play it safe? IV. Each of the sentences below contains ONE mistake. Underline the mistakes and correct them. (5 pts)Your answers :1. The rhinoceros is known for its distinctively horns, which continue to grow throughout the animal’s lifetime._________________ 2. Thanks to timely actions, some elephant populations, especially that in southern Africa, have recovered over the last decade._________________ 3. I have bought a present for my mother, and now I need some wrapped paper._________________4 . Joel giving up smoking has caused him to gain weight and become irritable withhis acquaintances._________________ 5. If you choose to work in Nepal, you will find a well - establishing programme, especially in the capital Kathmandu._________________
Dung dịch A là HCl có pH=3. Dung dịch B là dung dịch NaOH có pH = 12. Trộn A và B theo tỉ lệ 9:1 về thể tích thu được dung dịch C. Tính pH của C.
Giúp em với ạ em vote hết. Dạng bài câu điều kiện ạ đây là câu điều kiện loại 2.
Lm giúp mik với >< mik cần gấp NL: CHỈ làm câu b, c, d thôi nha
.....Canada,it always snows.....winter
mọi người giúp em với ạ em cảm ơn
Tìm ĐIều kiện xác định của các câu sau giúp mik vs ạaaaaaaaaa
Vẽ Zeref trong fairy tail đi ak
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