lim(x^2-1)/(2x^2-x-1)=lim(x-1)(x+1)/((x-1)(2x+1))=lim(x+1)/(2x+1)=2/3
(x+1)(x-1)= limit ------------- x-->1 (2x+1)(x-1) x+1= limit ------------- x-->1 2x+1=2/3