20.一元二次方程x2+(a2−1)x+(a−2)=0x^{2}+(a^{2}-1)x+(a-2)=0x2+(a2−1)x+(a−2)=0的一根比1大,另一根比1小,则实数aaa的取值范围是___−2<a<1-2<a<1−2<a<1___.