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\(\left(\frac{1}{7}x-\frac{2}{7}\right)\left(\frac{1}{5}x+\frac{3}{5}\right)\left(\frac{1}{3}x+\frac{4}{3}\right)=0\)

<=> \(\frac{x-2}{7}.\frac{x+3}{5}.\frac{x+4}{3}=0\)

<=> \(\frac{x-2}{7}=0\)hoặc \(\frac{x+3}{5}=0\); \(\frac{x+4}{3}=0\)

Nếu \(\frac{x-2}{7}=0\)<=> \(x-2=0\)<=> \(x=2\)
Nếu \(\frac{x+3}{5}=0\)<=> \(x+3=0\) <=> \(x=3\)

Nếu \(\frac{x+4}{3}=0\)<=> \(x+4=0\)<=> \(x=4\)

Vây x= 2 hoặc 3; 4

a: \(5x-20x^2=0\)

\(\Leftrightarrow5x\left(1-4x\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{4}\end{matrix}\right.\)

c: \(x\left(x-3\right)-5x+15=0\)

\(\Leftrightarrow\left(x-3\right)\left(x-5\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=5\end{matrix}\right.\)

bn nhờ bn này giúp nek

bn ấy hc giỏi toán hơn mk

https://olm.vn/thanhvien/cuoidoi09081002

xl bn nha

mẫu mấy câu: 

\(a,x^4y^4+4\)

\(=\left(x^2y^2+2\right)^2-4x^2y^2\)(cái này hok lâu sẽ tự hiêur)

\(=\left(x^2y^2-2xy+2\right)\left(x^2y^2+2xy+2\right)\)

\(a,x^4-x^2+2x-1=x^4-\left(x^2-2x+1\right).\)

\(=x^4-\left(x-1\right)^2=\left(x^2-x+1\right)\left(x^2+x-1\right)\)

\(b,x^4+x^3+x^2+1=??\text{ xem lại đề tí đi bn}+x\text{ nữa mói lm đc}\)

\(c,x^3-4x^2+4x-1=x^2\left(x-1\right)-3x\left(x-1\right)+\left(x-1\right)\)

\(=\left(x-1\right)\left(x^2-3x+1\right)\)

\(\frac{2}{2.3}+\frac{2}{3.4}+\frac{2}{4.5}+...+\frac{2}{x.\left(x+1\right)}=\frac{2008}{2010}.\)

\(2.\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2008}{2010}\)

\(\frac{1}{2}-\frac{1}{x+1}=\frac{502}{1005}\)

\(\frac{1}{x+1}=\frac{1}{2010}\)

=> x + 1 = 2010

=> x = 2009

Ta có : \(\frac{2}{2\times3}+\frac{2}{3\times4}+....+\frac{2}{x\times\left(x+1\right)}=\frac{2008}{2010}\)

\(\Rightarrow2\times\left(\frac{1}{2\times3}+.....+\frac{1}{x\times\left(x+1\right)}\right)=\frac{1004}{1005}\)

\(\Rightarrow2\times\left(\frac{1}{2}-\frac{1}{3}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{1004}{1005}\)

\(\Rightarrow\frac{1}{2}-\frac{1}{x+1}=\frac{1004}{1005}:2\)

\(\Rightarrow\frac{1}{2}-\frac{1}{x+1}=\frac{502}{1005}\)

\(\Rightarrow\frac{1}{x+1}=\frac{1}{2}-\frac{502}{1005}=\frac{1}{2010}\)

\(\Rightarrow x+1=2010\)

\(\Rightarrow x=2010-1=2009\)

3) |x(x-4)| = x

\(\Rightarrow\hept{\begin{cases}x\left(x-4\right)=x\\x\left(x-4\right)=-x\end{cases}}\Rightarrow\hept{\begin{cases}x-4=1\\x-4=-1\end{cases}}\Rightarrow\hept{\begin{cases}x=5\\x=3\end{cases}}\)

Vậy x = 3 hoặc x = 5