\(#TyHM\)

\(21,\\ e,PT\Leftrightarrow\left|2x-5\right|=5-2x\Leftrightarrow\left[{}\begin{matrix}2x-5=5-2x\left(x\ge\dfrac{5}{2}\right)\\5-2x=5-2x\left(x< \dfrac{5}{2}\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{2}\left(tm\right)\\0x=0\left(tm\right)\end{matrix}\right.\\ \Leftrightarrow x\in R\\ f,\Leftrightarrow\left|x-\dfrac{1}{4}\right|=\dfrac{1}{4}-x\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{1}{4}=\dfrac{1}{4}-x\left(x\ge\dfrac{1}{4}\right)\\\dfrac{1}{4}-x=\dfrac{1}{4}-x\left(x< \dfrac{1}{4}\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{4}\left(tm\right)\\0x=0\left(tm\right)\end{matrix}\right.\\ \Leftrightarrow x\in R\)

cùng ý kiến với bạn mình cũng chọn câu D 

d nha b

17[21-(-111)]+17[29-121]=17.132+17.(-92)=17.[132+(-92)]=17.40=680

Câu 21.

Độ dãn lò xo:

\(\Delta l=l-l_0=15-10=5cm=0,05m\)

Thế năng đàn hồi:

\(W_{đh}=\dfrac{1}{2}k\cdot\left(\Delta l\right)^2=\dfrac{1}{2}\cdot100\cdot0,05^2=0,125J\)

Chọn A

17 do you

18 shouldn't they

19 does she

20 can't he

21 will you

22 shouldn't they

23 does she

24 can they

25 doesn't it

17 do you

18 shouldn't they

19 does she

20 can't he

21 will you

22 shouldn't they

23 does she

24 can they

25 doesn't it

17. You don’t like playing games, do you ?

18. They should have been able to do it , shouldn't they ?

19. She doesn’t come here, dose she?

20. Tom can help her, can't he ?

21. You won’t be late, will you ?

22. The students should keep silent, shouldn't they ?

23. Mary seldom wears her dress, does she ?

24. Tom and Jerry can’t  live in peace, can they ?

25. The case weights thirty kilos, doesn't it ?

22.

\(sinx\le1\Rightarrow3sinx+2019\le3.1+2019=2022\)

Đáp án B

23.

\(C_n^3=\dfrac{A_n^3}{3!}=\dfrac{2022}{6}=337\)

Đáp án A