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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.
Your tutorials are good and you have a personality as well. I hope you have more advanced college level stuff, because I like the way you teach.”
Thanks alot for such great lectures... I never found learning this easier ever before... keep up the great work.... :)”
You seem so kind, it's awesome. Easier to learn from people who seem to be rooting for ya!' thanks”
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Sample Problems (22)
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Solving Quadratic Equations by Factoring
Problem 1 14,343 viewsSolve by factoring:
x² + 4x = 0 
Solving Quadratic Equations by Factoring
Problem 2 11,612 viewsSolve by factoring:
x² + 2x = 15 
Solving Quadratic Equations by Factoring
Problem 3 10,557 viewsSolve by factoring:
x² + 6x + 9 = 0 
Solving Quadratic Equations by Factoring
Problem 4 10,447 viewsSolve by factoring:
3x² − 18x = 27 
Solving Quadratic Equations by Factoring
Problem 5 1,341 views 
Solving Quadratic Equations by Factoring
Problem 6 1,327 views 
Solving Quadratic Equations by Factoring
Problem 7 1,161 views 
Solving Quadratic Equations by Factoring
Problem 8 1,156 views 
Solving Quadratic Equations by Factoring
Problem 9 1,113 views 
Solving Quadratic Equations by Factoring
Problem 10 1,168 views 
Solving Quadratic Equations by Factoring
Problem 11 1,060 views 
Solving Quadratic Equations by Factoring
Problem 12 1,056 views 
Solving Quadratic Equations by Factoring
Problem 13 1,058 views 
Solving Quadratic Equations by Factoring
Problem 14 1,173 views 
Solving Quadratic Equations by Factoring
Problem 15 995 views 
Solving Quadratic Equations by Factoring
Problem 16 385 views 
Solving Quadratic Equations by Factoring
Problem 17 422 views 
Solving Quadratic Equations by Factoring
Problem 18 361 views 
Solving Quadratic Equations by Factoring
Problem 19 402 views 
Solving Quadratic Equations by Factoring
Problem 20 390 views 
Solving Quadratic Equations by Factoring
Problem 21 377 views 
Solving Quadratic Equations by Factoring
Problem 22 300 views
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