Question

Answer 1

\(a,2+3x=20\\ \Rightarrow3x=18\\ \Rightarrow x=6\\ b,3x+7=3-x\\ \Leftrightarrow4x=-4\\ \Leftrightarrow x=-1\\ c,2x^3-8x=0\\ \Leftrightarrow2x\left(x^2-4\right)=0\\ \Leftrightarrow x\left(x-2\right)\left(x+2\right)=0\\ \Leftrightarrow \left[{}\begin{matrix}x=0\\x=2\\x=-2\end{matrix}\right.\)

Answer 2

\(a.3x=18\Leftrightarrow x=6\\ b.3x+x=3-7\Leftrightarrow4x=-4\Leftrightarrow x=-1\\ c.2x\left(x^2-4\right)=0\Leftrightarrow2x\left(x-2\right)\left(x+2\right)=0\Leftrightarrow x\in\left\{2;-2;0\right\}\)