What will be the condition for (a2 - 9)x2 + bx + c = 0 to be a quadratic equation?
For any quadratic equation of standard form ax2 + bx + c = 0 the condition is a,b,c should be real number and a≠0. So considering the same here a2 - 9 should not be zero.
a2 - 9 ≠0
a2 ≠ 9
So for above equation to be of degree 2, the coefficient of x2 should not be equal to zero, i.e. a≠3 and also a≠ -3.