+129771 x^2 - 2 > 0 (1)
(x - sqrt 2) ( x + sqrt 2) > 0 make into an equality
(x -sqrt 2) ( x + sqrt 2) = 0
x -sqrt 2 = 0 x + sqrt 2 = 0
x =sqrt 2 x = -sqrt 2
We have three possible solution intervals
(-inf, -sqrt 2) x = -2 is in this inerval and it makes (1) true
(-sqrt 2 , sqrt 2) x = 0 is in the interval and it makes (1) false
(sqrt 2, inf) x = 2 is in this interval and it makes (1) true
Answer
(-inf, sqrt 2) U ( sqrt 2, inf) = "d"
