$$(x+4)^2(x-5) = 40$$
Answer
$$ \begin{matrix}x_1 = 5.4481 & x_2 = -4.22405+2.04535i & x_3 = -4.22405-2.04535i \end{matrix} $$
Explanation
$$ \begin{aligned} (x+4)^2(x-5) &= 40&& \text{simplify left side} \\[1 em](x^2+8x+16)(x-5) &= 40&& \\[1 em]x^3-5x^2+8x^2-40x+16x-80 &= 40&& \\[1 em]x^3+3x^2-24x-80 &= 40&& \text{move all terms to the left hand side } \\[1 em]x^3+3x^2-24x-80-40 &= 0&& \text{simplify left side} \\[1 em]x^3+3x^2-24x-120 &= 0&& \\[1 em] \end{aligned} $$
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