Find roots of polynomial $$ p(x) = 90x^4+4x^3+21x^2+16x+21 $$
Answer
The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 0.4219+0.6352i\\[1 em]x_2 &= 0.4219-0.6352i\\[1 em]x_3 &= -0.4441+0.4518i\\[1 em]x_4 &= -0.4441-0.4518i \end{aligned} $$Explanation
Polynomial $ 90x^4+4x^3+21x^2+16x+21 $ has no rational roots that can be found using Rational Root Test, so the roots were found using quartic formulas.
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