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Ta có : \(3n-1⋮n-1\)
\(\Leftrightarrow3n-3+2⋮n-1\)
\(\Leftrightarrow3.\left(n-1\right)+2⋮n-1\)
\(\Leftrightarrow2⋮n-1\)
\(\Leftrightarrow n-1\inƯ\left(2\right)\)
Mà \(Ư\left(2\right)=\left\{1;-1;2;-2\right\}\)
\(\Rightarrow n-1\in\left\{1;-1;2;-2\right\}\)
\(\Rightarrow n\in\left\{2;0;3;-1\right\}\)
Vậy \(n\in\left\{2;0;3;-1\right\}\)
Chúc bạn học giỏi !!! Tham khảo cách của mk nha !!!
1/ The man spoke too fast for us to understand.
The man didn't ..... speak slowly enough for us to understand..........
2/ She is very old so she can't dance beautifully.
She is too ......old to dance beautifully...............
3/ Your writing is so small that I can't read it.
Your writing .....is too small for me to read........
4/ To learn English is easy.
It is ...........easy to learn English...............................................
5 / They think speaking French is difficult.
They think .......it is difficult to speak English...............
6/ It isn't easy to start looking for a job at his age.
Starting ..........looking for a job at his age isn't easy .........
7 / He is very old, so he can't apply for that job.
He is too... old to apply for that job................
8 / They ran too fast, so we couldn't catch them.
They ran too .....fast for us to catch ..........
9 / She spoke too quickly for me to understand.
She didn't .....speak slowly enough for me to understand......
10 / Mrs Hoa was too weak to go to work yesterday.
Mrs Hoa wasn't ....strong enough to go to work yesterday.......
11/ It is too cold, so we can't go out.
It is .........such a cold weather that we can't go out....................................
12/ He couldn't move the piano because it was too heavy.
The piano was ..too heavy for him to move
13 / Mrs Hoa was the last person who came to visit him.
Mrs Hoa....was the last person to come to visit him..........
Tổng số hạt trong M2X là 140, ta có:
\(\Rightarrow2\left[2P\left(M\right)+N\left(M\right)\right]+2P\left(X\right)+N\left(X\right)=140\)
\(\Leftrightarrow4P\left(M\right)+2P\left(X\right)+2N\left(M\right)+N\left(X\right)=140\) (1)
Số hạt mang điện nhiều hơn không mang điện là 44:
\(\Rightarrow4P\left(M\right)+2P\left(X\right)-\left[2N\left(M\right)+N\left(X\right)\right]=44\) (2)
Số khối của M{+} nhiều hơn X{2-} là 23:
\(\Rightarrow P\left(M\right)+N\left(M\right)-\left[P\left(X\right)+N\left(X\right)\right]=23\)
\(\Leftrightarrow P\left(M\right)-P\left(X\right)+N\left(M\right)-N\left(X\right)=23\) (3)
Tổng số hạt trong M{+} nhiều hơn trong X{2-} là 31:
\(\Rightarrow2P\left(M\right)+N\left(M\right)-1-\left[2P\left(X\right)+N\left(X\right)+2\right]=31\)
\(\Leftrightarrow2\left[P\left(M\right)-P\left(X\right)\right]+N\left(M\right)-N\left(X\right)=31\) (4)
Lấy (1) + (2) , ta có:
\(\Rightarrow8P\left(M\right)+4P\left(X\right)=184\) (5)
Lấy (4) - (3), ta có:
\(\Rightarrow P\left(M\right)-P\left(X\right)=11\) (6)
Từ 5; 6 \(\Rightarrow\orbr{\begin{cases}P\left(M\right)=9\\P\left(X\right)=8\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}M\text{ là }Kali\left(K\right)\\X\text{ là }Oxi\left(O\right)\end{cases}}\)
\(\Rightarrow M_2X\text{ là }K_2O\)
Số hạt mang điện trong hợp chất là (140+44)/2=92(hạt);
Số hạt mang điện trong M là (92-22)/2=35(hạt);
Số hạt mang điện trong X là (35+22)=57(hạt);
Phải, vì sau động từ khiếm khuyết chỉ có thể là một động từ nguyên mẫu không "to".
ai nhanh tay tôi cho 4
Vì A=\(\frac{12}{3n-1}\)\(\Rightarrow12⋮3n-1\Rightarrow3n-1\)là Ư(12)
Mà Ư(12) ={1;-1;2;-2;3;-3;4;-4;6;-6;12;-12}
Ta lập bảng
vậy n\(\in\){0;1;-1}
chúc bạn học tốt nha !