用两种方 法计算(x/x-2-x/x+2)*2-x/x
1个回答

请注意括号的正确使用,以免造成误解.

方法一:

[x/(x-2)-x/(x+2)][(2-x)/x]

=[1/(x-2)-1/(x+2)](2-x)

=-1-(2-x)/(x+2)

=[-(x+2)-(2-x)]/(x+2)

=(-x-2-2+x)/(x+2)

=-4/(x+2).

方法二:

[x/(x-2)-x/(x+2)][(2-x)/x]

=[1/(x-2)-1/(x+2)](2-x)

={[(x+2)-(x-2)]/[(x-2)(x+2)]}(2-x)

={4/[(x-2)(x+2)]}(2-x)

=-4/(x+2).

注:若原题不是我所猜测的那样,则请你补充说明.