1 have waited

2 has written

3 has studied

4 has finished

5 haven't done

6 We don't go to school on Saturdays.

7 They usually hold a party in New Year's Eve.

8 I've seen this film already.

9 Last night, she came home between 10.30 and 11 o'clock.

10 We are going to see the movie Dream City at 7.00 this evening.

1. have waited

2. has written

3. has studied

4. has finished

5 haven't done

6. We don't go to school on Saturdays

7. They usually hold a party on New Year's Eve

8. I have seen this film already

9. Last night she came home between 10.30 and 11 o'clock

10. We are going to see the movie Dream City at 7.00 this evening

\(ĐK:x\ne\dfrac{1}{2};x\ne1;x\ne\dfrac{3}{2};x\ne2;x\ne\dfrac{5}{2}\\ PT\Leftrightarrow\dfrac{1}{\left(2x-1\right)\left(x-1\right)}+\dfrac{1}{\left(x-1\right)\left(3x-2\right)}+\dfrac{1}{\left(3x-2\right)\left(x-2\right)}+\dfrac{1}{\left(x-2\right)\left(5x-2\right)}=\dfrac{4}{21}\\ \Leftrightarrow2\left[\dfrac{\dfrac{1}{2}}{\left(x-\dfrac{1}{2}\right)\left(x-1\right)}+\dfrac{\dfrac{1}{2}}{\left(x-1\right)\left(x-\dfrac{3}{2}\right)}+\dfrac{\dfrac{1}{2}}{\left(x-\dfrac{3}{2}\right)\left(x-2\right)}+\dfrac{\dfrac{1}{2}}{\left(x-2\right)\left(x-\dfrac{5}{2}\right)}\right]=\dfrac{4}{21}\)

\(\Leftrightarrow\dfrac{1}{x-1}-\dfrac{1}{x-\dfrac{1}{2}}+\dfrac{1}{x-\dfrac{3}{2}}-\dfrac{1}{x-1}+\dfrac{1}{x-2}-\dfrac{1}{x-\dfrac{3}{2}}+\dfrac{1}{x-\dfrac{5}{2}}-\dfrac{1}{x-2}=\dfrac{2}{21}\\ \Leftrightarrow\dfrac{1}{x-1}-\dfrac{1}{x-\dfrac{5}{2}}=\dfrac{2}{21}\\ \Leftrightarrow\dfrac{x-\dfrac{5}{2}-x+1}{\left(x-1\right)\left(x-\dfrac{5}{2}\right)}=\dfrac{2}{21}\\ \Leftrightarrow\dfrac{-\dfrac{3}{2}}{x^2-\dfrac{7}{2}x+\dfrac{5}{2}}=\dfrac{2}{21}\\ \Leftrightarrow x^2-\dfrac{7}{2}x+\dfrac{5}{2}=-\dfrac{63}{4}\\ \Leftrightarrow4x^2-14x+10=-63\\ \Leftrightarrow4x^2-14x+73=0\\ \Leftrightarrow x\in\varnothing\)

4.6

Ta có: \(\widehat{ABC}+\widehat{DCB}=180^0\)

mà hai góc này là hai góc ở vị trí trong cùng phía

nên AB//CD

a) A = \(\sum\limits^{50}_1\left(2x\right)-\sum\limits^{50}_1\left(2x-1\right)\) = 5050

b) B = \(\sum\limits^{2010}_1x^3\) = 4084663313000

 E, T, A, M: Mỗi chữ cái là một hình có trục đối xứng.

- Chữ I có hai trục đối xứng.

 Chữ N là hình không có trục đối xứng.

mỡi chữ cái là 1 hình trục đối xứng

5

V = V I - I

\(V=VI-I\)

VI = V - I

V = VI - I

VI = V + I

mình ko có đâu

KKKK

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