-х^4-4х^2+5=0 !!!!!!!!

- x^4 - 4x^2 + 5 = 0 
x^4 + 4x^2 - 5 = 0 
(x^2 + 5)(x^2 - 1) = 0 

x^2 = - 5
нет решений

x^2 = 1
x1 = - 1
x2 = 1