Answer:
Assuming you meant x² + 12x + 11, then it would be expressed as:
(x + 6)² - 25
Explanation:
The way you wrote the expression, the second term is not multiplied by x, and you wouldn't get the answer expected. It would just be x² + 33. Presumably that was in error and the 12 is in fact just a coefficient of x, so let's work from there.
x² + 12x + 11
= x² + 12x + 36 - 25
= (x + 6)² - 25