①(x^2/x+2-4/x+2)÷x-2/x
=(x-2)*x/(x-2)
=x
②x-1/x+2÷x^2-2x+1/x^2-4+1/x-1
=(x-2)/(x-1)+1/(x-1)
=(x-1)/(x-1)
=1
③没有括号把分子分母分开实在太难看明白了.