原式=[x+2/x(x-2) - x-1/(x-2)²] × x²(x-2)/x-4 =[(x+2)(x-2)/x(x-2)² - x(x-1)/x(x-2)²] × x²(x-2)/x-4 =x-4/x(x-2)² × x²(x-2)/x-4 =x/x-2
