find the roots of x3+6x2+11x+6=0 what is the formula and answer how to solve this ??

Answer 1

Even though a formula to solve a cubic equation exists, nobody in their right mind would use it
http://www.math.vanderbilt.edu/~schectex/courses/cubic/

The first thing I usually do is to try the factor theorem
look for factors of 6 which might work
try x = ±1, ±2, ±3

on my second try, I found x = -1 to be a root,
so x+1 is a factor

Use either long algebraic division or synthetic division to get the other factor of x^2 + 5x + 6
which factors once more to
(x+2)(x+3)

so ...
x^3+6x^2+11x+6=0
(x+1)(x+2)(x+3) = 0
x = -1, -2, -3

We were lucky for this to happen, if no nice rationals were found, we could use more advanced methods such as Newton's Method