x²-4=(x+2)(x-2)
4-2x=-2(x-2)
最简公分母是2(x+2)(x-2)
x²-4分之1=1/(x²-4)
=1/[(x+2)(x-2)]
=2/[2(x+2)(x-2)]
4-2x分之x=x/(4-2x)
=x/[-2(x-2)]
=x(x+2)/[-2(x+2)(x-2)]
= -x(x+2)/[2(x+2)(x-2)]