(2a^2-3a+1)/（1-a^2)÷(4a^2-4a+1)/(2a^2+a-1)
=[(2a-1)(a-1)/(1-a)(1+a)]×[(2a-1)(a+1)/(2a-1)²]
=-[(2a-1)/(1+a)]×[(a+1)/(2a-1)]
=-1