`a)(13x+39)(sqrt{14}-sqrt7x)=0`
`<=>` \(\left[ \begin{array}{l}13x+39=0\\\sqrt{14}-\sqrt7x=0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=-3\\x=\sqrt2\end{array} \right.\)
`b)(0,9x+1,54)(1,02-0,3x)=0`
`<=>` \(\left[ \begin{array}{l}0,9x=-1,54\\0,3x=1,02\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=-\dfrac{77}{45}\\x=\dfrac{17}{5}\end{array} \right.\)
`c)(x-2)(x^2-3x+5)=(x-2)x^2`
`<=>(x-2)(x^2-3x+5-x^2)=0`
`<=>(x-2)(5-3x)=0`
`<=>` \(\left[ \begin{array}{l}x=2\\x=\dfrac53\end{array} \right.\)
`d)2x^2+x=9-6x`
`<=>2x^2+7x-9=0`
`a+b+c=0`
`=>x_1=1,x_2=c/a=-9/2`
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