7.
\(①\)计算:\( \dfrac{2}{a+1}- \dfrac{a-2}{{a}^{2}-1}÷ \dfrac{{a}^{2}-2a}{{a}^{2}-2a+1} \)
\(②\)计算:\({2}^{2}+{\left(- \dfrac{1}{2}\right)}^{-2}-{3}^{-1}+ \sqrt{ \dfrac{1}{9}}+{\left(π-3.14\right)}^{0} \)
\(③\)解方程:\( \dfrac{3}{x-2}=2+ \dfrac{x}{2-x} \)