Answer:
The real solutions are -5, -4, 4, 5. There are no complex solutions.
Explanation:
The equation ...
... x^4 -41x^2 +400 = 0
can be factored as ...
... (x^2 -16)(x^2 -25) = 0
... (x -4)(x +4)(x -5)(x +5) = 0
So, all roots are real and are ...
... x ∈ {-5, -4, 4, 5}
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These are the values of x that make the factors zero.