x2square -100?

Answer 1

I suppose you need the factorisation:
x^2 - 100 = (x+10)(x - 10)

UPDATE: I think you meant (x^2)^2 and not x^2. I'm awfully sorry. Then the factorisation is:
(x^2)^2 - 100 = (x^2 + 10)(x^2 - 10)

Suppose the numbers equal zero:

(x^2)^2 - 100 = 0
(x^2)^2 = 100
x^2 = 10
x = square root of 10

Answer 2

(x^2)^2 - 100
= (x^2 - 10)*(x^2+10)
therefore
x^2 - 10 = 0
x^2 = 10
x = +/- sqrt(10)

and
x^2 + 10 = 0
x^2 = -10
x = +/- sqrt(-10)
x = +/- i*sqrt(10)

Therefore, the value of x are:
x = sqrt(10)
x = -sqrt(10)
x = i * sqrt(10)
x = -i * sqrt(10)

where i = sqrt(-1)

That's it.