The correct answer for this question is this one: x^2 - sqrt(7) ^ 2
So, how were we able to get that answer.
The question asked us to have an equation of difference of squares.
That means, it is in the form of
a^2 - b^2
Since, the given equation has
x^2 - 7, so we need to have something that is equal to seven
7 = sqrt(7)^2