已知x/2=y/5,求x+y/2x-5y的值

问题描述:

已知x/2=y/5,求x+y/2x-5y的值

x/2=y/5
x=2y/5
(x+y)/(2x-5y)
=(2y/5+y)/(2*2y/5-5y)
=(7y/5)/(-21y/5)
=-1/3