Hi everyone, my name is Leah and I'm taking an online College Algebra course at WCJC. I just need help understanding this question . Anything would be helpful.

Simplify the rational expression. Find all the numbers that must be excluded from the domain of the simplified rational expression.

x2 + 7x + 10/

x2 + 11x + 18

What i don't understand is the last part of the question, finding all the numbers that must be excluded. I know how to simplify rational expressions. Also it's multiple choice, so that kind of narrows it down, I just want to understand this.

Thanks.