# How do you use the rational root theorem to find the roots of #x^3+2x-9=0#?

##### 1 Answer

Sep 22, 2015

#### Answer:

The rational root theorem will only tell you what the possible rational roots are. This cubic has no rational roots.

#### Explanation:

By the rational root theorem, any rational root of

So the possible rational roots are:

#+-1# ,#+-3# ,#+-9#

None of these work.

Using Cardano's method, I found one Real root: