The values of 'a' for which a2−1x2+2(a−1)x+2 is positive for any x, are

We know that, the expression ax2+bx+c>0  for all x, if a >0 and b2 < 4ac∴a2−1x2+2(a−1)x+2 is positive for all x, ifa2−1>0  and 4(a−1)2−8a2−1<0⇒a2−1>0 and −4(a−1)(a+3)<0⇒a2−1>0 and  (a−1)(a+3)>0⇒ a2>1 and a<−3 or a>1⇒a<−3 or a>1