Ta có : 9x + 5y \(⋮\)17

=> 2(9x + 5y)  \(⋮\)17

=> 18x + 10y  \(⋮\)17

=> 18x + 27y - 17y  \(⋮\)17

=> 9(2x + 3y) - 17y  \(⋮\)17

Vì -17y \(⋮\)17

=> 9(2x + 3y)  \(⋮\)17

=> 2x + 3y  \(⋮\)17 (Vì 9 không chia hết cho 17)

9x+5y=17(x+y)-(8x+12y)=17(x+y)-4(2x+3y) chia hết cho 17

Mà 17(x+y) chia hết cho 17 => 4(2x+3y) chia hết cho 17 => 2x+3y chia hết cho 17 (dpcm)

1 + 2 + 3 + 4 + 5 +... + 200

SSH : (200 - 1) : 1 + 1 = 200

=> tổng : (1 + 200).200 : 2 = 20100

Vậy : ....

1 + 2 + 3 + ... + 200

Số số hạng của dãy là: \(\left(200-1\right)\div1+1=200\) (số)

Tổng bằng: \(\left(1+200\right).200\div2=20100\)

Vậy 1 + 2 + 3 + ... +200 = 20100.

Bạn vào câu hỏi tương tự là có nha !

Giải toán trên mạng - Giúp tôi giải toán - Hỏi đáp, thảo luận về toán học - Học toán với OnlineMath

Ko cs đầy đủ bn ơi!

Dãy số trên có số số hạng là :  \(\left(100-1\right)\div1+1=100\)    ( số )

Tổng dãy số là :     \(\frac{\left(100+1\right)\times100}{2}=5050\)

                  Đáp số : ...

\(\frac{\left[\left(100-1\right):1+1\right].\left(100+1\right)}{2}\)\(=5050\)

Chúc Bạn Hok Tốt l

Xét \(x< \frac{1}{4}\Rightarrow\hept{\begin{cases}4x-1< 0\\x-3< 0\end{cases}\Rightarrow}\hept{\begin{cases}\left|4x-1\right|=1-4x\\\left|x-3\right|=3-x\end{cases}}\)

Khi đó biểu thức : \(2\left|x-3\right|-\left|4x-1\right|=2\left(3-x\right)-\left(1-4x\right)=2x+5\)

Xét \(\frac{1}{4}\le x< 3\Rightarrow\hept{\begin{cases}4x-1\ge0\\x-3< 0\end{cases}\Rightarrow}\hept{\begin{cases}\left|4x-1\right|=4x-1\\\left|x-3\right|=3-x\end{cases}}\)

Khi đó biểu thức : \(2\left|x-3\right|-\left|4x-1\right|=2\left(3-x\right)-\left(4x-1\right)=-6x+7\)

\(x\ge3\Rightarrow\hept{\begin{cases}4x-1>0\\x-3\ge0\end{cases}\Rightarrow}\hept{\begin{cases}\left|4x-1\right|=4x-1\\\left|x-3\right|=x-3\end{cases}}\)

Khi đó biểu thức : \(2\left|x-3\right|-\left|4x-1\right|=2\left(x-3\right)-\left(4x-1\right)=-2x-5\)

TH1: Nếu \(x< \frac{1}{4}\)\(\Rightarrow\hept{\begin{cases}\left|x-3\right|=-\left(x-3\right)\\\left|4x-1\right|=-\left(4x-1\right)\end{cases}}\)

\(\Rightarrow2\left|x-3\right|-\left|4x-1\right|=-2\left(x-3\right)+\left(4x-1\right)\)

\(=-2x+6+4x-1=2x+5\)

TH2: Nếu \(\frac{1}{4}\le x\le3\)\(\Rightarrow\hept{\begin{cases}\left|x-3\right|=-\left(x-3\right)\\\left|4x-1\right|=4x-1\end{cases}}\)

\(\Rightarrow2\left|x-3\right|-\left|4x-1\right|=-2\left(x-3\right)-\left(4x-1\right)\)

\(=-2x+6-4x+1=-6x+7\)

TH3: Nếu \(x>3\)\(\Rightarrow\hept{\begin{cases}\left|x-3\right|=x-3\\\left|4x-1\right|=4x-1\end{cases}}\)

\(\Rightarrow2\left|x-3\right|-\left|4x-1\right|=2\left(x-3\right)-\left(4x-1\right)\)

\(=2x-6-4x+1=-2x-5\)

1.Our sources of energy will soon end if we don’t try to save them. 

=> Unless we try to save our sources of energy, they will soon end.

2. Barbare plays chess better than Mike.

=> Mike doesn’t play chess as well as Barbare.

3. Despite the silly story, many people enjoyed the film (although)

=> Although the story was silly, many people enjoyed the film.

4. Although the ket price was high, many people went to see that film. (However)

=> The ket price was high; however, many people went to see that film.

5. He performs very well, although he is young (Despite)

=> Despite being young, he performs very well.

6. It was a comedy, but I didn’t find it funny at all. (In spite of)

=> In spite of the fact that it was a comedy, I didn't find it funny at all.

7. The film was so boring. However, Jack saw it from beginning to end. (but)

=> The film was so boring but Jack saw it from beginning to end.

8.In spite of having a happy ending, the film begins with a terrible disaster.(although)

=> Although the film has a happy ending, it begins with a terrible disaster.

9. Although the film was a bit frightening, I really enjoyed it. (Despite)

=> Despite the fact that the film was a bit frightening, I really enjoyed it.

10. He is young, but he performs very well. (In spite of) 

=> In spite of being young, he performs very well.

Bg

48 + x - 30 = 36 - 2x

48 - 30 + x = 36 - 2x

18 + x        = 36 - 2x

        x        = 36 - 2x - 18

        x        = 36 - 18 - 2x

        x        = 18 - 2x

        x - x   = 18 - 2x - x

        0        = 18 - 3x

        18      = 3x

        18 : 3 = x

         6       = x

Bài làm 

\(48+x-30=36-2x\)

\(\Leftrightarrow-18+3x=0\Leftrightarrow x=\frac{18}{3}=6\)

đây là 51-a phần 69+a nha

dưới cũng vậy 

mik ghi sai

12.come

come/haven't lived

13. is raining

14. is

15. took

16. started

17. is playing

18. did/do

cycled/watch

Học tốt :))

III. Rewrite the sentences below, using the present perfect.

12/ Where you (come) ………come…………….from in Finland?

-I (come) ……come…….from Helinki. But I (not live) …haven't lived……there since I was ten years old.

13/ Look at the sky!. It (rain) ………is raining……………………………….

14/ The olympic Games ( be)…are……… held once every four years.

15/ The first olympic games (take)……took….. place in Greece in 776

16/ People (start)………started…. to use computer about 50 years ago.

17/ What ‘s that noise? - The children (play)………is playing…… tug of war.

18/ What …did……. you (do)……do…….. last weekend?

- I (cycle)……cycled………… round the lake with my friends.. Then I (watch) …watched……..TV in the afternoon.