x^4-8x^2+5=0
x^2=t
t^2-8t+5=0
D=64-20=44
t(1)=(8+√(44))/2
t(1)=(2*4+2√(11))/2
t(1)=(2*(4+√(11))/2
t(1)=4+√(11)
t(2)=(8-√(44))/2
t(2)=(2*4-2√(11))/2
t(2)=(2*(4-√(11))/2
t(2)=4-√(11)
x^2=4+√(11) или x^2=4-√(11)
t^2-8t+5=(t-4+√(11))*(t-4-√(11))
(t-4+√(11))*(t-4-√(11))=(t-4)^2-11
(t-4)^2-11=(x^2-4)^2-11=(x-2)*(x+2)-11
y=(x-2)*(x+2)-11