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Mathematics 17 Online
OpenStudy (anonymous):

Which of the binomials below is a factor of this trinomial? 3x2 + 18x - 21

jimthompson5910 (jim_thompson5910):

First factor out the GCF 3 3x^2+18x-21 3(x^2+6x-7) Then find two numbers that multiply to -7 and add to 6.

OpenStudy (anonymous):

is it 3

OpenStudy (anonymous):

x-3 or x+3

jimthompson5910 (jim_thompson5910):

is a factor, but it's not a binomial

jimthompson5910 (jim_thompson5910):

so the answer isn't 3

OpenStudy (anonymous):

ok then the answer is 1

jimthompson5910 (jim_thompson5910):

no

jimthompson5910 (jim_thompson5910):

that's not a binomial either

OpenStudy (anonymous):

ok im going to put the choices that they give me

jimthompson5910 (jim_thompson5910):

alright

OpenStudy (anonymous):

x - 3 x + 1 x - 1 x + 3

jimthompson5910 (jim_thompson5910):

look at x^2+6x-7 what two numbers multiply to -7 and add to 6

OpenStudy (anonymous):

im lost

jimthompson5910 (jim_thompson5910):

what are the factors of 7

OpenStudy (anonymous):

(x+1) (x-7)

jimthompson5910 (jim_thompson5910):

you are close, but -7+1 = -6 NOT +6

OpenStudy (anonymous):

so then its +7?

jimthompson5910 (jim_thompson5910):

good, (x-1)(x+7)

OpenStudy (anonymous):

thank you

jimthompson5910 (jim_thompson5910):

sure thing

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