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