Being wrong is okay.

You must have one cardinal, unbreakable, totally accepted rule in your classroom.
IT'S OKAY TO BE WRONG!!!.
NEVER, under any circumstances, ridicule or be sarcastic to a learner who makes a mistake.

We all make mistakes, and nothing destroys a person's desire to try, faster than public ridicule.

If you want your students to do math willingly and with enthusiasm, never ridicule a student for giving a wrong answer. Find something good about their response, then rephrase the question or modify it in a different way and ask them again. This gives the individual a chance to publicly redeem themselves and not feel stupid. It also sets a tone of respect and safety in your classroom that will be appreciated. You will get a great deal more participation if everyone knows that they are not in danger of ridicule.

A nice result of this rule will be that your students will extend the same respect to you. When you screw up, and you will, they will politely correct you and the atmosphere of trust will be protected.

If you, the teacher, violate this rule even one time, you will lose the trust of your students and the environment in your classroom will deteriorate immediately. You will see the students shut down. They will instantly believe that if you can embarrass one student you can do it to them too. So NEVER VIOLATE THIS RULE!!!

If for some reason, like lack of sleep or complete frustration, you let a rude or sarcastic comment pass from your lips, your only hope is to publicly acknowledge your mistake and apologize to the student you insulted in front of the others. Make sure you are sincere too or it will worsen the insult. Most people will give you one more chance if you are willing to publicly admit your mistake. But again, these infractions must be very rare or you will lose the trust of your whole class.