Your factoring was correct. However, if it is desired to factor the polynomial into monomials using complex or irrational roots, you need to keep going with the x^2 + 11 term; nothing can be done with the x^3 term unless the homework is expecting you to write this as x * x * x
x^2 + 11 = (x + √11 i)(x - √11 i)
Then, depending on what the assignment is looking for, the answer is either x^3(x + √11 i)(x - √11 i) or
x*x*x*(x + √11 i)*(x - √11 i)