Find roots of polynomial $$ p(x) = 6x^3-21x^3-7 $$
Answer
The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -0.7757\\[1 em]x_2 &= 0.3878+0.6717i\\[1 em]x_3 &= 0.3878-0.6717i \end{aligned} $$Explanation
Step 1:
Combine like terms:
$$ \color{blue}{6x^3} \color{blue}{-21x^3} -7 = \color{blue}{-15x^3} -7 $$Step 2:
Polynomial $ -15x^3-7 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.
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