首页 > 留学知识库

问题: 先化简再求值

x/(x-2)÷[2+x-4/(2-x)] 其中x=1/2

解答:

x/(x-2)÷[2+x-4/(2-x)]
=[x/(x-2)]/[(x+2)+4/(x-2)]
=[x/(x-2)]/{[(x+2)(x-2)+4]/(x-2)}
=[x/(x-2)]*{(x-2)/[(x+2)(x-2)+4]}
=x/(x^2-4+4)
=x/x^2
=1/x
=1/(1/2)
=2