giúp e đi em xin mng đấy ạ
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g: \(=\dfrac{x^2+2x-x^2-4x-2x+4}{x\left(x-2\right)\left(x+2\right)}=\dfrac{-4x+4}{x\left(x-2\right)\left(x+2\right)}\)
h: \(=\dfrac{2x^2+1-x^2+1-x^2+x-1}{\left(x+1\right)\left(x^2-x+1\right)}\)
\(=\dfrac{x+1}{\left(x+1\right)\left(x^2-x+1\right)}=\dfrac{1}{x^2-x+1}\)
\(e,=\dfrac{1}{x-1}-\dfrac{2x}{\left(x^2+1\right)\left(x-1\right)}=\dfrac{x^2-2x+1}{\left(x^2+1\right)\left(x-1\right)}=\dfrac{\left(x-1\right)^2}{\left(x^2+1\right)\left(x-1\right)}=\dfrac{x-1}{x^2+1}\\ f,=\dfrac{3x-1}{2\left(3x+1\right)}+\dfrac{3x+1}{2\left(3x-1\right)}-\dfrac{6x}{\left(3x-1\right)\left(3x+1\right)}\\ =\dfrac{9x^2-6x+1+9x^2+6x+1-12x}{2\left(3x-1\right)\left(3x+1\right)}=\dfrac{2\left(3x-1\right)^2}{2\left(3x-1\right)\left(3x+1\right)}=\dfrac{3x-1}{3x+1}\)
\(g,=\dfrac{x}{x\left(x-2\right)}-\dfrac{x^2+4x}{x\left(x-2\right)\left(x+2\right)}-\dfrac{2}{x\left(x+2\right)}\\ =\dfrac{x^2+2x-x^2-4x-2x+4}{x\left(x-2\right)\left(x+2\right)}=\dfrac{-4x+4}{x\left(x-2\right)\left(x+2\right)}\\ h,=\dfrac{2x^2+1-x^2+1-x^2+x-1}{\left(x+1\right)\left(x^2-x+1\right)}=\dfrac{x+1}{\left(x+1\right)\left(x^2-x+1\right)}=\dfrac{1}{x^2-x+1}\)
11. If you knew Japanese, you would understand what I mean.
→ Were ........you to know Japanese, you would understand what I mean.....................................................
12. If I were a bird, I would fly.
→ Were ..........I a bird, I would fly. ..................................................
13. If you had trained harder, you would have won the game.
→ Had ....you trained harder, you would have won the game.........................................................
14. If I were you, I would not behave in such a polite manner in front of my boss.
→ Were .......I you, I would not behave in such a polite manner in front of my boss......................................................
15. If I studied at a prestigious university, I would have the opportunity to work abroad.
→ Were ........I to study at a prestigious university, I would have the opportunity to work abroad. ....................................................
16. If he has a temperature, he will see the doctor.
→ Should..........he have a temperature, he will see the doctor...................................................
17. If my friends come, I will be very happy.
→ Should.........my friend come, I will be very happy....................................................
18. If she had earned a lot of money, she would have flown to New York.
→ Had .....she earned a lot of money, she would have flown to New York.......................................................
19. If I knew your father, I would tell him to help you practice harder.
→ Were............I to know your father, I would tell him to help you practice harder.................................................
20. If she needs some more money, she can take an extra 200.
→ Should.......she need some more money, she can take an extra 200.....................................................
Bài 1:
\(a,\dfrac{25}{14x^2y}=\dfrac{75y^4}{42x^2y^5};\dfrac{14}{21xy^5}=\dfrac{28x}{42x^2y^5}\\ b,\dfrac{3x+1}{12xy^4}=\dfrac{3x\left(3x+1\right)}{36x^2y^4};\dfrac{y-2}{9x^2y^3}=\dfrac{4y\left(y-2\right)}{36x^2y^4}\\ c,\dfrac{1}{6x^3y^2}=\dfrac{6y^2}{36x^3y^4};\dfrac{x+1}{9x^2y^4}=\dfrac{4x\left(x+1\right)}{36x^3y^4};\dfrac{x-1}{4xy^3}=\dfrac{9x^2y\left(x-1\right)}{36x^3y^4}\\ d,\dfrac{3+2x}{10x^4y}=\dfrac{12y^4\left(3+2x\right)}{120x^4y^5};\dfrac{5}{8x^2y^2}=\dfrac{75x^2y^3}{120x^4y^5};\dfrac{2}{3xy^5}=\dfrac{80x^3}{120x^4y^5}\)
1: \(\left(x+2y\right)^2=x^2+4xy+4y^2\)
2: \(\left(2x+3y\right)^2=4x^2+12xy+9y^2\)
3: \(\left(3x-2y\right)^2=9x^2-12xy+4y^2\)
Biết mỗi câu 1 thôi :v : Trích trong vb Mẹ tôi của Ét-môn-đô-đơ A-mi-xi
Cho cả năm luôn này cj:) Ngữ pháp tiếng Anh lớp 8 cả năm - Hiến thức tiếng Anh lớp 8 học kì 1 + học kì 2 - VnDoc.com
Ta có: \(\frac{x+2}{y+10}\)\(=\)\(\frac{1}{5}\)\(\Rightarrow\)\(5\left(x+2\right)=y+10\)(1)
\(y-3x=2\)\(\Rightarrow\)\(y+2=3x\) (2)
Thay (2) vào (1) ta có:
\(5\left(x+2\right)=\left(y+2\right)+8\)
\(5x+10=3x+8\)
\(5x-3x=8-10\)
\(2x=-2\)
\(x=-2:2\)
\(x=-1\)
Vậy: x=-1
Chúc bạn làm bài tốt!
Bài 5:
d: Áp dụng tính chất của dãy tỉ số bằng nhau, ta được:
\(\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{4}=\dfrac{x+y-z}{2+3-4}=\dfrac{-20}{1}=-20\)
Do đó: x=-40; y=-60; z=-80
\(1,=\left(x-3\right)^2\\ 2,=\left(5+x\right)^2\\ 3,=\left(\dfrac{1}{2}x+2b\right)^2\\ 4,=\left(\dfrac{1}{3}-y^4\right)^2\\ 5,=\left(x+2y\right)\left(x^2-2xy+4y^2\right)\\ 6,=\left(2y-5\right)\left(4y^2+10y+25\right)\\ 7,=\left(a^2-b\right)\left(a^4+a^2b+b^2\right)\\ 8,=\left(x-5\right)^2\\ 9,=8\left(x^3-\dfrac{1}{64}\right)=8\left(x-\dfrac{1}{4}\right)\left(x^2+\dfrac{1}{4}x+\dfrac{1}{16}\right)\)
Bn dùng hằng đẳng thức đáng nhớ nhé.
Thêm một chút kiên thức về bài:
\(\left(\dfrac{a}{b}\right)^2=\dfrac{a^2}{b^2}\)
\(a^{xy}=\left(a^x\right)^y\)