\(a,2x^2-18x+28=0\)
\(\Leftrightarrow2\left(x^2-9x+14\right)=0\)
\(\Leftrightarrow x^2-9x+14=0\)
\(\Leftrightarrow\left(x-7\right)\left(x-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-7=0\\x-2=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=7\\x=2\end{matrix}\right.\)
\(b,\dfrac{x-2}{x^2-9}+\dfrac{3x-1}{x+3}=\dfrac{2x+1}{x-3}+1\left(ĐKXĐ:x\ne\pm3\right)\)
\(\Leftrightarrow\dfrac{x-2}{\left(x-3\right)\left(x+3\right)}+\dfrac{\left(3x-1\right)\left(x-3\right)}{\left(x-3\right)\left(x+3\right)}-\dfrac{\left(2x+1\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}-1=0\)
\(\Leftrightarrow\dfrac{x-2}{\left(x-3\right)\left(x+3\right)}+\dfrac{3x^2-10x+3}{\left(x-3\right)\left(x+3\right)}-\dfrac{2x^2+7x+3}{\left(x-3\right)\left(x+3\right)}-\dfrac{\left(x-3\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}=0\)\(\Rightarrow x-2+3x^2-10x+3-2x^2-7x-3-x^2+9=0\)
\(\Leftrightarrow-16x+7=0\)
\(\Leftrightarrow-16x=-7\)
\(\Leftrightarrow x=\dfrac{7}{16}\left(tm\right)\)
\(VậyS=\left\{\dfrac{7}{16}\right\}\)
a: =>x^2-9x+14=0
=>(x-2)(x-7)=0
=>x=2 hoặc x=7
b: =>x-2+(3x-1)(x-3)=(2x+1)(x+3)+x^2-9
=>x-2+3x^2-9x-x+3=2x^2+7x+3+x^2-9
=>3x^2-9x+1=3x^2+7x-6
=>-16x=-7
=>x=7/16
