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Factoring Trinomials, a = 1  Problem 3
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
This problem I have a trinomial where my b value is negative but c is positive. Keep in mind this is the product of my two values, this is their sum. I’m looking for two numbers that multiply to a positive answer but add up to a negative answer. That means I’m looking for two negative values. A negative times a negative is a positive and when I add them up I also have a negative answer, so now I need to think of what 2 numbers multiply to 10, add up to 7 and there both going to be negative numbers.
Well things that multiply to 10 are either 1 or 10. That’s not going to work because they don’t ever add up to anything close to 7. Or 5 and 2: in our case 5 and 2, because is need them to add up to a negative number and multiply to a positive number. There they are. That’s my factored form.
I’m going to go through and FOIL just to check; firsts, outers, inners, lasts. And I can already see in my brain when I combine those middle terms I will have 7. That’s how I know it's right. I just wanted to show you guys one of the tricks of how to approach these problems. It gets a lot trickier when you don’t have a 1, if you have like a 2 or something there. So it’s important that you spend time now looking for patterns when you have positives and negatives showing up in your coefficients.
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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.
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Sample Problems (11)
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Factoring Trinomials, a = 1
Problem 1 14,371 viewsFactor:
x² + 12x + 20 
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Problem 2 9,998 viewsFactor:
p² + 3p − 10 
Factoring Trinomials, a = 1
Problem 3 8,709 viewsFactor:
m² − 7m + 10 
Factoring Trinomials, a = 1
Problem 4 7,755 viewsFactor:
x² + 9x − 20 
Factoring Trinomials, a = 1
Problem 5 1,520 views 
Factoring Trinomials, a = 1
Problem 6 1,172 views 
Factoring Trinomials, a = 1
Problem 7 1,158 views 
Factoring Trinomials, a = 1
Problem 8 1,112 views 
Factoring Trinomials, a = 1
Problem 9 1,539 views 
Factoring Trinomials, a = 1
Problem 10 1,024 views 
Factoring Trinomials, a = 1
Problem 11 1,350 views
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