\(a,5x-20=0\\ \Leftrightarrow5x=20\\ \Leftrightarrow x=4\\ b,2\left(x+3\right)+13=4\left(3-2x\right)\\ \Leftrightarrow2x+6+13=12-8x\\ \Leftrightarrow10x=12-13-6\\ \Leftrightarrow10x=-7\\ \Leftrightarrow x=-\dfrac{7}{10}\\ c,\left(x-12\right)\left(2x+9\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x-12=0\\2x+9=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=12\\x=-\dfrac{9}{2}\end{matrix}\right.\\ d,\dfrac{2}{x+5}=\dfrac{3}{2x-7}\)
\(ĐK:\left\{{}\begin{matrix}x\ne-5\\x\ne\dfrac{7}{2}\end{matrix}\right.\\ \Leftrightarrow2.\left(2x-7\right)=3.\left(x+5\right)\\ \Leftrightarrow4x-14=3x+15\\ \Leftrightarrow x=29\left(t/m\right)\)
a)
`5x-20=0`
`<=>5x=20`
`<=> x=4`
b)
`2(x+3)+13=4(3-2x)`
`<=> 2x+6+13=12-8x`
`<=> 2x+8x=12-6-13`
`<=> 10x=-7`
`<=> x=-7/3`
c)
`(x-12)(2x+9)=0`
\(< =>\left[{}\begin{matrix}x-12=0\\2x+9=0\end{matrix}\right.\\ < =>\left[{}\begin{matrix}x=12\\x=-\dfrac{9}{2}\end{matrix}\right.\)
d)
\(\dfrac{2}{x+5}=\dfrac{3}{2x-7}\left(x\ne-5;x\ne\dfrac{7}{2}\right)\)
`<=> 2(2x-7)=3(x+5)`
`<=> 4x-14=3x+15`
`<=> 4x-3x=15+14`
`<=> x=29`
