(x^4-x^2-90)/x^4

Solution for (x^4-x^2-90)/x^4 equation:

D( x )

x^4 = 0

x^4 = 0

x^4 = 0

1*x^4 = 0 // : 1

x^4 = 0

x = 0

x in (-oo:0) U (0:+oo)

(x^4-x^2-90)/(x^4) = 0

(x^4-x^2-90)/(x^4) = 0 // * x^4

x^4-x^2-90 = 0

t_1 = x^2

1*t_1^2-1*t_1^1-90 = 0

t_1^2-t_1-90 = 0

DELTA = (-1)^2-(-90*1*4)

DELTA = 361

DELTA > 0

t_1 = (361^(1/2)+1)/(1*2) or t_1 = (1-361^(1/2))/(1*2)

t_1 = 10 or t_1 = -9

t_1 = -9

x^2+9 = 0

1*x^2 = -9 // : 1

x^2 = -9

t_1 = 10

x^2-10 = 0

1*x^2 = 10 // : 1

x^2 = 10

x^2 = 10 // ^ 1/2

abs(x) = 10^(1/2)

x = 10^(1/2) or x = -10^(1/2)

x in { 10^(1/2), -10^(1/2) }