Find roots of polynomial $$ p(x) = -r^3-64r+128 $$
Answer
The roots of polynomial $ p(r) $ are:
$$ \begin{aligned}r_1 &= 1.8939\\[1 em]r_2 &= -0.9469+8.1664i\\[1 em]r_3 &= -0.9469-8.1664i \end{aligned} $$Explanation
Polynomial $ -r^3-64r+128 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.
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