Question 9 of 15 for which of the following equations are x = 3 x=3 and x = − 3 x=−3 both solutions? (the 2s next to the x are x to the power of 2 int the choice)
a)x2−3x−9=0
b)x2+9=0
c)x2+6x−9=0
d)x2−9=0

For option D, x²-9,
if you apply the identity[(a²-b²)=(a+b)(a-b)] it will give you (x+3)(x-3)=0,
here two things are possible if (x-3)is the zero,3 I.e. x=3, then the equation is true
or
(x+3) is 0, I.e. x=-3.
And rest of the equation don't have real roots!