Question 768727
The request implies the cubic expression is equated to 0.


Checking the root, -3 with synthetic division, the quotient is x^2-2x-1.  The REAL and rational root is x=-3. 


The synthetic division supporting this is:


-3___|____1____1____-7____-3
_____|____ ___-3____6_____3
_____|______________________
__________1___-2____-1____0----------see, the remainder is 0.




If you work further with the resulting quadratic, you'll find the irrational roots {{{1-sqrt(2)}}} and {{{1+sqrt(2)}}}.