已知b/a=1/2,则(2a+b/2a-b)-4b/a-b的值是
问题描述：
已知b/a=1/2,则(2a+b/2a-b)-4b/a-b的值是
答
(2a+b)/(2a-b)-4b/(a-b)=(2a/a+b/a)/(2a/a-b/a)-(4b/a)/(a/a-b/a)=(2+b/a)/(2-b/a)-4/(1-b/a)=(2+1/2)/(2-1/2)-4/(1-1/2)=(5/2)/(3/2)-4/(1/2)=5/3-4*2=5/3-8=5/3-24/3=-19/3