a, 2-x=2(x-2)²
⇔2-x=2(2-x)²
⇔1=2(2-x)
⇔2-x=`1/2`
⇒x=`3/2`
b,8x³-72x=0
⇔8x(x²-9)=0
⇔$\left[\begin{matrix} 8x=0\\ (x-3)(x+3)=0\end{matrix}\right.$
⇔$\left[\begin{matrix} x=0\\x-3=0 \\x+3=0\end{matrix}\right.$
⇔$\left[\begin{matrix} x=0\\ x=3\\x=-3\end{matrix}\right.$
c,$(x-5)^{4}$ -(5-x)²=0
⇔[(x-5)²]²-(x-5)²=0
⇔(x-5)².[(x-5)²-1²]=0
⇔$\left[\begin{matrix} (x-5)^2=0\\(x-5)^2-1^2=0\end{matrix}\right.$
⇔$\left[\begin{matrix} x-5=0\\ (x-6)(x-4)=0\end{matrix}\right.$
⇔$\left[\begin{matrix} x=5\\ x=4\\x=6\end{matrix}\right.$
