求下题：(3a^2-15a+21)/(a^2-5a+6)-(2a^2-6a+1)/(a^2-3a+2)
问题描述：
求下题：(3a^2-15a+21)/(a^2-5a+6)-(2a^2-6a+1)/(a^2-3a+2)
答
(3a²-15a+21)/(a²-5a+6)-(2a²-6a+1)/(a²-3a+2)=3+3/(a²-5a+6)-2+3/(a²-3a+2)=1+3/(a-3)-3/(a-2)+3/(a-2)-3/(a-1)=1+3/(a-3)-3/(a-1)