Dan factored x^2+121 into (x+1-11)

Your question is a little unclear. If you are just trying to factor x² + 121, it's prime. (can't be factored using real numbers).

Step-by-step explanation:

The difference of two squares is a special form. a² - b² = (a+b) (a-b).

But, the sum of two squares is prime. a² + b² cannot be factored.