Answer:

Step-by-step explanation:
120cm^3
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X⁴ - 81 = x⁴ - 9² (Difference of 2 squares, then we an write it:
(x²-3)(x²+3) =0, → then (x²-3) = 0 and (x²+3)=0
(x²-3) = 0 → x² = 3 → x = +√3 and x = -√3
(x²+3) =0 → x² = -3 → x = +√-3 and x = -√3→ or i√3 AND x = -i√3
A{ -3 , +3 , -i√3 , i√3}