[(a+1)/(a方-a)+4/(1-a方)]除以(a方+2a-3)/(a方+3a) 其中a=-5/3

题目

[(a+1)/(a方-a)+4/(1-a方)]除以(a方+2a-3)/(a方+3a) 其中a=-5/3

答案

(a+1)/(a^2-a)+4/(1-a^2)=(a+1)/(a^2-a)-4/(a^2-1)=(a+1)/[a(a-1)]-4/[(a+1)(a-1)]=[(a+1)^2-4a]/[a(a+1)(a-1)]=(a-1)^2/[a(a+1)(a-1)]=(a-1)/[a(a+1)](a^2+2a-3)/(a^2+3a)=(a-1)(a+3)/[a(a+3)]=(a-1)/a所以原式={(a...