Answer:
The answers A,B,D and E are verified.
Step-by-step explanation:
We have equation, x⁴ - 3 x² + 2 = 0
Substituting y = x²
So equation is y²- 3 y+ 2 = 0
=> (y-1)(y-2) = 0
y = 1 or y = 2
So we have x² = 1 or x² = 2
=> x = 1 , x = -1 ,
or

So the answers are A,B,D and E.