Posted by jenny on Monday, October 15, 2012 at 4:52pm.
x3+6x2+18x+13=0

maths  Steve, Monday, October 15, 2012 at 5:08pm
unless ±1 or ±13 is a root, you're stuck.
It's easy to show that 1 is a root. So, you have
(x+1)(x^2+5x+13)
Now you gotta solve the quadratic, but that's old hat by now.