Make a generalization for the error found inx²+9=(x+3)(x+3)

If we are talking about a triangle with two sides being of equal length: 11, then you can use Pythagorean Theorem to solve.  

Step-by-step explanation:

Imagine the sides labeled as a, b, and c. a and b are both 11. We have to find the value of c. we can do this by writing a^2+b^2=c^2. so 11^2+11^2=c^2. All that is left to do is find the square root of c^2 and you are left with your answer.