# Thread: how to factor out?

1. ## how to factor out?

$r^3-r^2-r-1 = 0$

From given equation, how to solve for r? please show me step by step.

2. Originally Posted by zpwnchen
$r^3-r^2-r-1 = 0$

From given equation, how to solve for r? please show me step by step.
as written, the cubic will not factor ... the single real root is irrational. A decimal approximation can be found using technology or you can use this ...

Cubic Formula -- from Wolfram MathWorld