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

Thank you for watching the video.

To unlock all 5,300 videos, start your free trial.

Solving Quadratic Equations by Factoring - Problem 2

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

Share

All right here’s a problem that I want to solve by factoring. But before I can factor this I need to get this equation that’s equal to 0. I need to subtract 15 from both sides before I can do any factoring. x2 plus 2x take away 15 equals 0. Now I’m looking for two numbers whose product is -15 and whose sum is +2.

So you guys have already practiced factoring a lot you know that the numbers I’m going to want to use are +5 and -3. You know where I did that it’s kind of like Foiling in my head I would have as my outsides 5x, my insides will be -3x added together I get +2x.

Okay now I’m going to use the zero product property and write each one of these terms as equal to 0 and then solve for x to find my solutions. Add 3 to both sides and I would have x equals 3, subtract 5 from both sides and I would have x equals -5.

I think those are my solutions let me just check up top. Make sure that when you substitute in 3, 3² is 9 plus 2, 2 times 3 is 6 it should be equal to 15 good let’s test with -5. -5² is 25, -5 times 2 is -10 and I do indeed get 15 as my answer that told me I did this problem correctly. So solving by factoring what you want to do is make sure that your original problem is set equal to 0 before you do any factoring over here on your trinomial.

© 2023 Brightstorm, Inc. All Rights Reserved. Terms · Privacy