$$2x^3+4x^2-5-(4x^3-x^2+3x+12) = 0$$
Answer
$$ \begin{matrix}x_1 = -1.30975 & x_2 = 1.90487+1.69153i & x_3 = 1.90487-1.69153i \end{matrix} $$
Explanation
$$ \begin{aligned} 2x^3+4x^2-5-(4x^3-x^2+3x+12) &= 0&& \text{simplify left side} \\[1 em]2x^3+4x^2-5-4x^3+x^2-3x-12 &= 0&& \\[1 em]-2x^3+5x^2-3x-17 &= 0&& \\[1 em] \end{aligned} $$
This polynomial has no rational roots that can be found using Rational Root Test.
Roots were found using qubic formulas.
This page was created using
Polynomial Equations Solver