Answer: x = {+-sqrt(3), +-2*sqrt(3)}.
Step-by-step explanation:
(x^2 - 8)^2 + (x^2 - 8) = 20
▪︎ Let (x^2 - 8) be y.
Then,
y^2 + y = 20
y^2 + y - 20 = 0
D = b^2 - 4ac = 1 + 20*4 = 81 = 9^2
y1 = (-b - sqrt(D))/(2a) = (-1 - 9)/2 = -10/2 = -5
y2 = (-b + sqrt(D))/(2a) = (-1 + 9)/2 = 8/2 = 4
1) x^2 - 8 = -5
x^2 = 8 - 5
x^2 = 3
x = +-sqrt(3)
2) x^2 - 8 = 4
x^2 = 8 + 4
x^2 = 12
x = +-sqrt(12)
x = +-2*sqrt(3)
