a)\(3x\left(x^2-2\right)+x^2\left(1-2x\right)-x^2=0\)
\(\Leftrightarrow x\left(3x^2-6+x-2x^2-x\right)=0\)
\(\Leftrightarrow x\left(x^2-6\right)=0\)
\(\Rightarrow\left\{{}\begin{matrix}x=0\\x^2-6=0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=0\\x=\sqrt{6}\end{matrix}\right.\)
b)\(4x\left(x-1\right)-3\left(x^2+5\right)-x^2=0\)
\(\Leftrightarrow4x^2-4x-3x^2-15-x^2=0\)
\(\Leftrightarrow-4x-15=0\)
\(\Rightarrow4x=15\)
\(\Rightarrow x=\dfrac{15}{4}=3,75\)
c)\(\left(3x-1\right)\left(2x+7\right)-\left(x+1\right)\left(6x-5\right)=\left(x+2\right)-\left(x-5\right)\)
\(\Leftrightarrow6x^2+21x-2x-7-6x^2+5x-6x+5=7\)
\(\Leftrightarrow18x=9\)
\(\Rightarrow x=\dfrac{1}{2}\)
