There are only two terms in this expression that are alike: 3xy and -6xy.
is , so our simplified expression will be:
Example 2
Simplify:
The parentheses in this expression are not necessary, since it doesn't change how we treat each expression. We can rewrite it without 'em, then mark each set of like terms.
The tricky part with this problem is to keep the correct addition and subtraction signs with each term. Combine everything and we get our final answer.
Example 3
Simplify:
There are two things to be careful with in this problem.
First, each term in the second expression is being subtracted, so we've gotta "distribute" the subtraction sign to each term when removing the parentheses.
Notice also that when we distribute the negative sign to another negative sign, it becomes addition. Now we'll mark our like terms.
The second thing we need to be cautious with is the last term, b. Even though it doesn't show a coefficient, it's the same as 1b.
is 
, so our simplified expression will be:
