Question

1, 7x - 4 = 3x + 20 2, 2x - 5^2 - x + 2^2 = 0 3, 2/x+1 + 1 = 7/x+1

Answer 1

\(1,7x-4=3x+20\\ \Leftrightarrow7x-4-3x-20=0\\ \Leftrightarrow4x-24=0\\ \Leftrightarrow x=6\\ 2,2x-5^2-x+2^2=0\\ \Leftrightarrow x-25+4=0\\ \Leftrightarrow x-21=0\\ \Leftrightarrow x=21\\ 3,ĐKXĐ:x\ne-1\\ \dfrac{2}{x+1}+1=\dfrac{7}{x+1}\\ \Leftrightarrow\dfrac{2}{x+1}+\dfrac{x+1}{x+1}-\dfrac{7}{x+1}=0\\ \Leftrightarrow\dfrac{2+x+1-7}{x+1}=0\\ \Rightarrow x-4=0\\ \Leftrightarrow x=4\left(tm\right)\)

Answer 2

1. \(7x-4=x+20\)

\(\Leftrightarrow7x-x=20+4\)

\(\Leftrightarrow6x=24\Leftrightarrow x=4\)

Vậy : ...

 

2. \(\left(2x-5\right)^2-\left(x+2\right)^2=0\)

\(\Leftrightarrow\left(2x-5+x+2\right)\left(2x-5-x-2\right)=0\)

\(\Leftrightarrow\left(3x-3\right)\left(x-7\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}3x-3=0\\x-7=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=7\end{matrix}\right.\)

Vậy : ...