Question

Solve the following equation:
$x^3+72x-1720=0$.

Answer 1

Given equation, $x^3+72x-1720=0$

$⟹x^3+10x^2-10x^2+172x-100x-1720=0⟹(x-10)(x^2+10x+172)=0$

Solving the quadratic equation, we have $x=-5\pm 7\sqrt{3}i$

$\therefore$ roots of the given equation are $x=10,-5\pm 7\sqrt{3}i$