第一种方法,括号内先通分：
{3x/(x-2)-x/(x+2) } (x^2-4)/x
= {3x(x+2)-x(x-2) } /{(x+2)(x-2) * (x+2)(x-2)/x
= {3x^2+6x-x^2x+2x } /{(x+2)(x-2) * (x+2)(x-2)/x
= {2x^2+8x} /{(x+2)(x-2) * (x+2)(x-2)/x
= 2x {x+4} /{(x+2)(x-2) * (x+2)(x-2)/x
= 2(x+4)
= 2x+8
第二种方法,先破括号：
{3x/(x-2) - x/(x+2) } (x^2-4)/x
= 3x/(x-2) * (x^2-4)/x - x/(x+2) * (x^2-4)/x
= 3x/(x-2) * (x+2)(x-2)/x - x/(x+2) * (x+2)(x-2)/x
= 3 (x+2) -(x-2)
= 3x +6 -x+2
= 2x+8