Doing expressions and equations is something that you do as you move up in the levels of algebra. Do expressions and equations with help from an experienced math professional in this free video clip.

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Doing expressions and equations is something that you do as you move up in the levels of algebra. Do expressions and equations with help from an experienced math professional in this free video clip.

Part of the Video Series: Math Skills

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Hi, I'm Drew Moyer. And this is how to do expressions and equations. As a student moves up into higher levels of algebra, we should be able to solve more complex equations with more complex expressions built into those equations. Lets take a look at our example. We have two-X minus seven over X cubed plus six-X squared minus eight-X, times three X cubed plus 18-X-squared minus 24-X over three-X plus 24 is equal one. The first thing I want to do, is treat each numerator and denominator as a problem all its own and I want to factor those problems. So, I have two minus seven, unfortunately I can't factor anything out of that. So, we'll leave that alone. But down here, I see that I have an X in common with all three terms. So, I can pull that out. So, X and then, goes inside, we have X-squared plus six-X minus eight, times, now up here, on this numerator, I see that I have a three-X in common. So, I'm going to go ahead and pull those out. And left on the inside, I have X-squared plus six-X minus eight. And down here, I only have a three in common. So, I can go ahead and pull that out as well. And on the inside, I have X plus eight is equal to one. So, now I see that I have quite a few things that I can cross cancel. For example, I have this big trinomial right here, X-squared plus six-X minus eight. And again, over here, X-squared plus six-X minus eight. Which means that I can cancel them both out. Another thing I van cancel out is this three, that I see right here and down here. And if it's in the numerator and the denominator, then that means I can cancel it out. The last thing that I see that I can cancel is this X right here, can cancel with this X over here. And it looks like that's about it. So, now I'm just going to multiply my simplified expression straight across, numerator to numerator and denominator to denominator. So, on the top, all I'm left with is this two-X minus seven and on the bottom, all I'm left with this is X plus eight. And it's still equal to one. But I know that if something is divided by something else and it equals one. Then I know that those two somethings must equal each other. So, I have two-X minus seven is equal to X plus eight. And from here it's very easy to solve. I'm going to subtract X from both sides. Which leaves me with X minus seven equals eight. And then, simply add seven to both sides. And I'm left with X is equal to 15. So, I'm Drew Moyer, and that is how to do expressions and equations.