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Solving Quadratic Equations by Factoring  Problem 4
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 I have a problem that I want to solve by factoring and there’s a couple of things that are making me nervous. The first thing is that it's not in standard form and the second thing is I have a whole bunch of big coefficients. So I’m hoping there might be a greatest common factor.
Let’s start by writing this guy equal to 0 by subtracting 27 from both sides. This stuff stays the same, then I have 27 is equal to 0. Now I’m going to look for a greatest common factor. Greatest common factor meaning a combination of numbers and letters that multiplies into to all three of these terms.
Well you guys can probably tell that 3 goes into all of these I could either factor out 3 or 3. I’m going to factor out 3 just being really careful with the minus signs. If I factor out 3 like undistributing I’ll have 3 times +6x and times +9 equal to 0.
Now I’m not done factoring yet because this trinomial can be factored even further. 3 times (x plus 3), (x plus 3).
My last step is to use the last product properly but this is one is kind of tricky because I have three things being multiplied together that give me the answer 0. So I could kind of write 3 equal 0 and x plus 3 equals 0 and x plus 3 equals 0, although this is never true right? That means I’m not going to get a solution out of there you don’t even need t worry about the greatest common factor it doesn’t affect my x solutions.
Once I’ve gotten rid of that guy I also notice that the same binomial shows up twice. This is a perfect square trinomial, so that tells me I’m only going to have one answer that answer is going to be x equals 3. The only value that makes this statement true is the value 3. To check you would go back and substitute 3 in here for both Xs and make sure that your answer does indeed give you +27.
When you are doing these problems look for a greatest common factor like this and if it’s just a constant like 3, it’s not going to give you any solution you can just kind of cancel that guy out it doesn’t affect your final solutions here.
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Alissa Fong
M.A. in Secondary Mathematics, Stanford University
B.S., Stanford University
Alissa has a quirky sense of humor and a relatable personality that make it easy for students to pay attention and understand the material. She has all the math tips and tricks students are looking for.
Sample Problems (22)
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Solving Quadratic Equations by Factoring
Problem 1 15,320 viewsSolve by factoring:
x² + 4x = 0 
Solving Quadratic Equations by Factoring
Problem 2 12,416 viewsSolve by factoring:
x² + 2x = 15 
Solving Quadratic Equations by Factoring
Problem 3 11,184 viewsSolve by factoring:
x² + 6x + 9 = 0 
Solving Quadratic Equations by Factoring
Problem 4 11,338 viewsSolve by factoring:
3x² − 18x = 27 
Solving Quadratic Equations by Factoring
Problem 5 1,773 views 
Solving Quadratic Equations by Factoring
Problem 6 1,740 views 
Solving Quadratic Equations by Factoring
Problem 7 1,518 views 
Solving Quadratic Equations by Factoring
Problem 8 1,446 views 
Solving Quadratic Equations by Factoring
Problem 9 1,434 views 
Solving Quadratic Equations by Factoring
Problem 10 1,476 views 
Solving Quadratic Equations by Factoring
Problem 11 1,337 views 
Solving Quadratic Equations by Factoring
Problem 12 1,423 views 
Solving Quadratic Equations by Factoring
Problem 13 1,342 views 
Solving Quadratic Equations by Factoring
Problem 14 1,539 views 
Solving Quadratic Equations by Factoring
Problem 15 1,334 views 
Solving Quadratic Equations by Factoring
Problem 16 696 views 
Solving Quadratic Equations by Factoring
Problem 17 713 views 
Solving Quadratic Equations by Factoring
Problem 18 611 views 
Solving Quadratic Equations by Factoring
Problem 19 661 views 
Solving Quadratic Equations by Factoring
Problem 20 654 views 
Solving Quadratic Equations by Factoring
Problem 21 662 views 
Solving Quadratic Equations by Factoring
Problem 22 656 views
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