M = ( x + 1 )³ - x³ + 1 - 3x( x + 1 )

= x³ + 3x² + 3x + 1 - x³ + 1 - 3x² - 3x

= 2 

Vậy M không phụ thuộc vào biến ( đpcm )

N = ( 2x - 1 )³ - 6x( 2x - 1 )² + 12x²( 2x - 1 ) - 8x³

= [ ( 2x - 1 ) - 2x ]³ ( HĐT số 4 )

= [ 2x - 1 - 2x ]³

= [ -1 ]³ = -1

Vậy N không phụ thuộc vào biến ( đpcm )

\(A=\left\{0,1,2,3\right\}\)

vì \(\hept{\begin{cases}X\subset A\\X\subset B\end{cases}}\)nên \(X=\left\{a\in R|a\ge0\right\}\)

Vì \(\left|x-y-2\right|\ge0\forall x;y\) ; \(\left|x+3\right|\ge0\forall x\)

\(\Rightarrow\left|x-y-2\right|+\left|x+3\right|\ge0\)

Dấu "=" xảy ra \(\Leftrightarrow\orbr{\begin{cases}\left|x-y-2\right|=0\\\left|x+3\right|=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x-y=2\\x=-3\end{cases}}\Leftrightarrow\orbr{\begin{cases}y=-5\\x=-3\end{cases}}\)

Vậy cặp số x ; y thỏa mãn đề bài là : ( - 3 ; - 5 )

\(\text{Theo bài ra, ta có}:\)

\(\hept{\begin{cases}a+b=402\\a:b=9\text{(dư 2)}\end{cases}}\)\(=>\hept{\begin{cases}a+b=402\left(1\right)\\a=9b+2\left(2\right)\end{cases}}\)

\(\text{Thay a=9b+2 vào phương trình (1), ta có:}\)

\(9b+2+b=402\)

\(=>10b=400\)

\(=>b=40\)

\(a=9b+2=9.40+2=362\)

\(\text{Vậy a=362 ; b=40}.\)

\(4:5:6=\frac{x}{4}=\frac{y}{5}=\frac{z}{6}\)

áp dụng tính chất dãy tỉ số bằng nhau ta được

\(\frac{x}{4}=\frac{y}{5}=\frac{z}{6}=\frac{x+y+z}{4+5+6}=\frac{30}{15}=2\)

x=4.2=8

y=5.2=10

z=6.2=12

vậy x=8  y=10    z=12

\(3xC=\frac{3}{1x2x3x4}+\frac{3}{2x3x4x5}+...+\frac{3}{97x98x99x100}\)

\(3xC=\frac{4-1}{1x2x3x4}+\frac{5-2}{2x3x4x5}+...+\frac{100-97}{97x98x99x100}\)

\(3xC=\frac{1}{1x2x3}-\frac{1}{2x3x4}+\frac{1}{2x3x4}+\frac{1}{3x4x5}+...+\frac{1}{97x98x99}-\frac{1}{98x99x100}\)

\(3xC=\frac{1}{1x2x3}-\frac{1}{98x99x100}\Rightarrow C=\frac{\frac{1}{6}-\frac{1}{98x99x100}}{3}\)

Bánh sinh nhật của mình 😋

trả lời đầy đủ

\(\frac{4}{9}:\left(x+0,4\right)=\frac{2}{3}=>\left(x+0,4\right)=\frac{4}{9}:\frac{2}{3}=>\left(x+0,4\right)=\frac{2}{3}=>x=\frac{2}{3}-0,4=>x=\frac{4}{15}\)

vậy \(x=\frac{4}{15}\)

\(\left|\frac{2}{7}-x\right|=1\frac{1}{3}=\orbr{\begin{cases}\left|\frac{2}{7}-x\right|=\frac{4}{3}\\\left|\frac{2}{7}-x\right|=-\frac{4}{3}\end{cases}}=>\orbr{\begin{cases}x=\frac{2}{7}-\frac{4}{3}\\x=\frac{2}{7}+\frac{4}{3}\end{cases}}=>\orbr{\begin{cases}x=-\frac{22}{21}\\x=\frac{34}{21}\end{cases}}\)

vậy \(\orbr{\begin{cases}x=-\frac{22}{21}\\x=\frac{34}{21}\end{cases}}\)

13 They've finished (do) their homework__doing

14 They had their house ( paint) before Tet holiday__painted

15 I advised him ( wait) for me at the airport__waiting

16 Would you mind (help) me with this work?__helping
17 Do you smell something (burn) in the chicken ?__burning

18 Mother requests her daughter not (come) back home late__come

19 We  shall have the grass (cut) tomorrow__cutting

20 They noed lots of sheep(graze) in green meadows___

21 When I'm tired , I enjoy (watch) TV . It's relaxing__watching

22 Would you (have) something to eat?_have
23 It started (rain)  an hour ago. Has it stopped (rain) yet?___rained__raining
24 My family is trying ( decide) where to go on holiday_decided

25 our teacher made me (answer) all the questions__answered

26 I've enjoy (meet) you . I hope (see) you again____meeting__see

27 I hate (see) a child (cry)__to see_crying

28 they prefer (play) in swimming pool all day___playing

29 the refuse(go) out on trips if it's too hot___to go

30 i used (smoke) 20 cigarettes a day , but now I give up (smoke)____smoked__smoking

31 We decided ( rent) a house with a swimming pool____

32 can you help me ( get ) the dinner ready ?__getting
33 when we arrived , the people next door invited us (have) a drink with them____having

34 We began (talk) about next year's holiday two months ago____talking

35 I remember (lock) the door when I left but forgot (shut) the window_______locked_shutting

36 He agrees (start) the job as soon as possible____started

37 I finished (read) the book and went to bed_____reading

38 My teachers always expected me (do)  well in exams_____to do

39 Let me ( pay) for the meal . You paid last time___paying

40 It's difficult (get) used to (eat) with chopsks_____got_eating