Posted by Anonymous on .
f(x) = x3 + 2x2 – 0.4X – 1
how do you you factor this?

Math 209 
Reiny,
Do not repost a question which has been answered.
http://www.jiskha.com/display.cgi?id=1276043019 
Math 209 
drwls,
Please use ^ before exponents.
There is no simpl standard formula for finding the roots of cubic equations. First create integer coefficients by rewriting as
(1/5) (5x^3 + 10x^2 2x 5)
There are no simple factors with integers for this equation. That can be proven with something sometimes called the "p/q theorem". It can be faotored to
f(x) = 5[(x0.689)(x+1.941,(x+0.748)]
I used an online solver for that.
The numbers in the factors are rounded.