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(49.50.51):3+1/2x=40642
41650+1/2x=40642
1/2x=40642-41650
1/2x=-1008
x=-1008:1/2
x=-2016
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1:
Ta có: \(4-2\left(x+1\right)=2\)
\(\Leftrightarrow2\left(x+1\right)=2\)
\(\Leftrightarrow x+1=1\)
hay x=0
Bài 2:
Ta có: \(\left|2x-3\right|-1=2\)
\(\Leftrightarrow\left|2x-3\right|=3\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-3=3\\2x-3=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=6\\2x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\x=0\end{matrix}\right.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
A=1/1.2+1/2.3+...1/x =49/50
A=1-1/2+1/2-1/3+...+1/x-1-1/x=49/50
A=1-1/x=49/50
A=50/50-1=x=49/50
x=1/50
\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{x}=\frac{49}{50}\)
\(\Rightarrow\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{x\left(x-1\right)}=\frac{49}{50}\)
\(\Rightarrow1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x-1}-\frac{1}{x}=\frac{49}{50}\)
\(\Rightarrow1-\frac{1}{x}=\frac{49}{50}\)
\(\Rightarrow\frac{1}{x}=\frac{1}{50}\)
\(\Rightarrow x=50\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) (x - 2).3⁵ = 3⁷
x - 2 = 3⁷ : 3⁵
x - 2 = 3²
x - 2 = 9
x = 9 + 2
x = 11
b) x² - 2x = 0
x(x - 2) = 0
⇒ x = 0 hoặc x - 2 = 0
*) x - 2 = 0
x = 2
Vậy x = 0; x = 2
c) (2x - 1)² = 49
⇒ 2x - 1 = 7 hoặc 2x - 1 = -7
*) 2x - 1 = 7
2x = 7 + 1
2x = 8
x = 8 : 2
x = 4
*) 2x - 1 = -7
2x = -7 + 1
2x = -6
x = -6 : 2
x = -3
Vậy x = -3; x = 4