Find roots of polynomial $$ p(x) = -x^3+4x+3x-9 $$
Answer
The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -3.1409\\[1 em]x_2 &= 1.5705+0.6317i\\[1 em]x_3 &= 1.5705-0.6317i \end{aligned} $$Explanation
Step 1:
Combine like terms:
$$ -x^3+ \color{blue}{4x} + \color{blue}{3x} -9 = -x^3+ \color{blue}{7x} -9 $$Step 2:
Polynomial $ -x^3+7x-9 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.
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