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![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có M = 1 + 2 + ..........+ 2^49
2M = 2 + 2^2 +.........+ 2^50
2M - M = (2 +2^2+.............+2^50) -(1 +2+.............+ 2^49)
M = 2^50 - 1
Mà M +1 = 2^n
<=> (2^50-1) +1 = 2^n
<=> 2^50 = 2^n
=> n = 50
Chúc bạn học tốt
![](https://rs.olm.vn/images/avt/0.png?1311)
\(Q=1+2+2^2+...+2^{49}\)
\(\Rightarrow2Q=2.\left(1+2+2^2+...+2^{49}\right)\)
\(\Rightarrow2Q=2+2^2+2^3+...+2^{50}\)
\(\Rightarrow2Q-Q=2+2^2+2^3+...+2^{50}-\left(1+2+2^3+...+2^{49}\right)\)
\(\Rightarrow Q=2+2^2+2^3+...+2^{50}-1-2-2^3-...-2^{49}\)
\(\Rightarrow Q=2^{50}-1\)
Thay \(Q=2^{50}-1\)vào \(Q+1=2^n\), ta có:
\(2^{50}-1+1=2^n\)
\(\Rightarrow2^{50}=2^n\)
\(\Rightarrow n=50\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a ,
\(x.x^2.x^3.x^4.x^5......x^{49}.x^{50}.x=x^{24.\left(1+49\right)+51}=x^{1251}\)
a) x . x2 . x3 . ... . x50
= x(1 + 2 + 3 + ... + 50)
= x1275
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
2)
a)Ta có: 2m+5=n.(m-1)
=> 2m+5=nm-n
=>2m+5-nm+n=0
=>(2-n).m+5+n=0
=>(2-n).m-(2-n)+5+2=0
=>(2-n).(m-1)+7=0
=>(2-n).(m-1)=-7=-1.7=-7.1
Ta có bảng sau:
2-n | 1 | -7 | -1 | 7 |
n | 1 | 9 | 3 | -5 |
m-1 | -7 | 1 | 7 | -1 |
m | -6 | 2 | 8 | 0 |
Vậy (n,m)=(1,-6),(9,2),(3,8),(-5,0)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{m}{2}-\frac{2}{n}=\frac{1}{2}\)
\(\Rightarrow\frac{2}{n}=\frac{m}{2}-\frac{1}{2}=\frac{m-1}{2}\)
=> n(m-1)=2.2
=>n(m-1)=4
=> n và m-1 \(\inƯ\left(4\right)=\left\{-1;-2;-4;1;2;4\right\}\)
Ta có bảng
n | m-1 | m |
1 | 4 | 5 |
4 | 1 | 2 |
-1 | -4 | -3 |
-4 | -1 | 0 |
2 | 2 | 3 |
-2 | -2 | -1 |
Vậy các cặp (m,n)\(\in Z\)là:................
Ta có:\(\frac{m}{2}-\frac{2}{n}=\frac{1}{2}\)
\(\Rightarrow\frac{mn}{2n}-\frac{4}{2n}=\frac{n}{2n}\)
\(\Rightarrow mn-4=n\)
\(\Rightarrow mn-n=4\)
\(\Rightarrow n.\left(m-1\right)=4\)
Làm nốt nha
![](https://rs.olm.vn/images/avt/0.png?1311)