At about the 0:59 mark, the teacher puts parentheses on the board, but he changes the meaning of the expression by putting them where he does; the expression should look like: (x^2y-ax)-(xy-a) OR (x^2y-ax)+(-xy+a).
In this lesson, you'll learn how to simplify an expression with four terms by factoring. First, you'll identify what each term shares in common. If none of the terms share a factor, you can try factoring by grouping. You'll then take the first two terms and the last two terms and look for a factor that can be factored out of both of them. Once you've factored out the common factor, you'll be left with two terms that are exactly the same. You can then factor out those two terms to simplify the expression.
Simplify an expression with four terms by factoring
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