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Mathematics 24 Online
OpenStudy (anonymous):

Need help with factoring trinomial's!

OpenStudy (anonymous):

\[a ^{2} - a - 20\]

hartnn (hartnn):

can you find 2 numbers with product = -20 and sum =-1 ??

OpenStudy (anonymous):

-5 & 4?

OpenStudy (anonymous):

-5*4 = -20 -5 + 4 = -20

OpenStudy (anonymous):

Right?

hartnn (hartnn):

thats correct! so, split -a as -5a +4a we have , \(a^2 -5a+4a-20=0\) factor out a from first 2 terms and 4 from last 2 terms , what u get ?

OpenStudy (anonymous):

Ummm

OpenStudy (anonymous):

Not sure . . .

OpenStudy (anonymous):

Wouldn't you just leave it as -5 & 4?

hartnn (hartnn):

\(a^2-5a = a (a-5)\) looks good ?

hartnn (hartnn):

no...

OpenStudy (anonymous):

Ok . . . I guess that looks good

OpenStudy (anonymous):

Thanks

hartnn (hartnn):

4a-20 =4(...?.. )

hartnn (hartnn):

i wasn't done yet :P

OpenStudy (anonymous):

Utterly confused . . .

hartnn (hartnn):

\(a^2-5a+4a-20 = a(a-5)+4(a-5)\\=(a-5)(a+4)\) now factoring is complete

OpenStudy (anonymous):

Ok . . .

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