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Solving Quadratic Equations Using Square Roots - 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 quadratic equation that I need to solve. Looking at it I notice right away there’s no b term. There’s nothing that has just one x attached to it. I have an x² term but nothing with x.

So what I’m going to do, is try taking the square roots to both sides of the equation. First I want to get x² all by itself, add 225 to both sides so I'll have x² equals to 225.

Next thing if I want x all by itself right now x is being squared the opposite of squaring is to take the square root. So I would say x is equal to the positive or negative of square root of 225. Please don’t forget this plus or minus business that’s really important. You guys might know that the square 225 is 15. So x equals 15 or -15. That’s my final solution and the way I would check is by going up here and making sure 15 times itself takes away 225 is 0 and also -15 times itself take away 225 is 0.

That’s it these problems are not so bad. When you see a quadratic equation that has an x² as the highest power and there is no b term, go ahead and get it so that you can take the square to both sides, it’s pretty easy.

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