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Solving Quadratic Equations by Factoring - Problem 1

Teacher/Instructor Alissa Fong
Alissa Fong

MA, Stanford University
Teaching in the San Francisco Bay Area

Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts

Here's a problem that I want to solve by factoring. So even if I don't know what solve means I know I’m going to have to start this problem by factoring. Since both of these terms have an x I’m going to factor out the greatest common factor which is x, it’s going to start looking like this. Like un-distributing. X times what gives me x squared? And then I need x times what gives me 4x here we go so that's my factored form of that binomial.

Next thing I’m going to do in order to solve, solve means find what x values make the statement true. So what I’m going to do in order to do that is use this 0 product property that tells me that if the product of two things is equal to 0 then either of that first guys is equal to 0 or the second guy is equal to 0.

That's already going to be one of my solutions if x is 0 that should be equal to 0.My other solution is going to be -4. Because if I plug in -4 here and I do out the math I should get 0. I'm going to check just a little really quickly just to make sure.

The way to check is by substituting the x value to this original problem. Is it true that 0 squared plus 4 times 0 is 0? Yeah 0 plus 0 equals 0. Is it true that -4times itself plus 4 times -4 is equal to 0? It’s kind of messy plus 4 times -4 is it true that 16 take away 16 equals 0? Yeah that's right.

That's how I know I have my two correct solutions. So when you’re asked to solve something by factoring factor out your binomial trinomial looking for greatest common factor or by using factoring techniques then set each one equal to 0. And lastly be sure to check your work because there's no reason why you want to get these problems wrong because they are not too difficult.

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