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Factoring Trinomials, a = 1 - Problem 4

6,918 views
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

This problem is kind of like a trick problem. Have you seen why? What I’m asked to do is find two numbers that multiply to -20 and add up to 9. Let’s check it out.

Some possibilities for 20, for things that multiply to 20 are 1 and 20, 2 or 10 or 4 and 5. But neither one of those are 9 apart. This is a trick problem. In fact we would say this is not factorable or this trinomial can not be factored. This is our answer. It is like this problem cannot be done.

This happens sometimes, sometimes you get combinations of numbers where nothing multiplies to that and adds up top that. Be really careful. Sometimes something that looks like it’s not factorable would be factorable if I had a number other than 1 as my leading coefficient, so look out for that.

This is only the case where I’m looking for the product and the sum if my leading coefficient is 1. Sometimes you get the answer not factorable. That’s okay, don’t freak out. That’s just something that happens in your Math class sometimes. There’s no answer.

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