Question 1013017
.
let y=x^2 
.
x^4-3x^2=4
x^4-3x^2-4=0 Replace x^2 with y.
y^2-3y-4=0
(y-4)(y+1)=0
.
y-4=0 or y+1=0
y=4 or y=-1 . Replace y with x^2
x^2=4 . or . x^2=-1
x=+/-2 . or . x=+/-i  . ({{{sqrt(-1)=i}}}