Completing the square can seem a little confusing at first, and trust me, everyone makes mistakes sometimes! Here are some common problems to watch out for when you’re doing it:

1. Forgetting to Divide: If you see a number in front of your $x^2$ term that isn't 1, make sure to factor it out first! For example, with $2x^2 + 8x$, pull out the 2:

   $$2(x^2 + 4x)$$

   Now you can complete the square for $x^2 + 4x$.

2. Not Halving the Coefficient: When you complete the square, you need to take half of the number in front of $x$, square it, and add it inside the brackets. If you forget to divide by 2, you’ll get the wrong answer!

3. Losing Track of Constants: After you add a number to complete the square, don’t forget to keep the equation balanced! If you add something inside the brackets, you need to subtract it outside if you factored out a number at the start. This can make things complicated!

4. Confusing Signs: Make sure to check your signs carefully! When you’re dealing with negative numbers, adding or subtracting can change the signs in your final answer.

5. Not Expanding to Check Your Work: It's sometimes worth it! After you think you’ve completed the square correctly, expand it back out to see if you get back to the original equation. This can help you find small mistakes.

By being aware of these common mistakes, you’ll see that completing the square becomes a lot easier! Happy math-ing!