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Mathematics 16 Online
OpenStudy (anonymous):

Help TOpic: Factoring Trinomials

OpenStudy (anonymous):

Question 1: \[9x ^{2}+9x-10\] A:\[(3x-5)(3x+2)\] B: \[(3x+5)(3x-2)\] C: \[(3x-1)(3x+10)\] D: Not Factorable Question 2: \[10x ^{2}+19x+6\] A: \[(2x+5)(3+2x)\] B: \[(5x+2)(2x+3)\] C: \[(2x-5)(3-2x)\] D: Not Factorable

OpenStudy (anonymous):

Question 3: \[18x ^{2}-54x+112\] A:\[(9x+2)(2x-56)\] B:\[(9x-2)(2x+56)\] C:\[(9x+2)(2x+56)\] D:Not Factorable

OpenStudy (bioepic):

Question 1 is B.

OpenStudy (xapproachesinfinity):

No answer dear @BioEpic, Against Open Study rules

OpenStudy (anonymous):

Question 4: \[3x^{2}-x-10\] A:\[(3x-2)(x+5)\] B:\[(3x+2)(x-5)\] C:\[(x-2)(3x+5)\] D: Not Factorable Question 5: \[8x ^{2}+22x+5\] A:\[(2x-5)(4x-1)\] B:\[(2x+5)(4x+1)\] C:\[(2x+5)(4x-1)\] D: Not Factorable Question 6: \[14x ^{2}-13x+5\] A:\[(7x-1)(2x+5)\] B:\[(7x-5)(2x+1)\] C:\[(-7x-1)(2x+5)\] D: Not Factorable

OpenStudy (xapproachesinfinity):

to factor a Trinomial if it factorable think about \((a+b)(a+c)=a^2+ac+ab+bc=a^2+a(b+c)+bc\) so think about two numbers that multiply to give you \(bc\) and add up to give you \(b+c\)

OpenStudy (xapproachesinfinity):

hey! one question at a time! for more question you have to open new thread. However your question are all same kind so one will be enough, the others you have to do them yourself after seeing how to do it

OpenStudy (xapproachesinfinity):

let's go with Q1 \(9x ^{2}+9x-10\) this trinomial if it is foctorable it would look this way \(9x ^{2}+9x-10=(9x~~~~~~~ )(x~~~~~~)\) the empty space if for the missing numbers and signs where did i get 9x and x you might ask! it is because the leading coefficient is 9 and the power 2 so it would be x times x 9x times x gives \(9x^2\) so for that reason we chose that

OpenStudy (xapproachesinfinity):

Are you following?

OpenStudy (anonymous):

yeh

OpenStudy (xapproachesinfinity):

to know what are the numbers we are missing we ask what are the two numbers that multiply to give us -10 at the same time add up to 9 to answer such a question we look at factors of 10 {1,2,5,10} if we pick 2 and 5 they won't work since they don't add up to 9 in any case 1 and 10 is the right choice then! \(-1\times10=-10\) \(-1+10=9\) if i choose -10 and 1 i would get \(-10\times1=-10\) \(-10+1=-9\) but we are not looking for -9 we are looking for 9 so -1 and 10 are the correct choice then we go back to our parenthesis \(9x ^{2}+9x-10=(9x\color{red}{-1})(x+\color{red}{10})\) this way it is wrong since we weill get 90x-x =89x not 9x so the right order is \(9x ^{2}+9x-10=(9x-\color{blue}{10})(x+\color{blue}{-1})\)

OpenStudy (xapproachesinfinity):

opps mistake \(9x ^{2}+9x-10=(9x+\color{blue}{10})(x\color{blue}{-1})\) i meant to put this way the last line

OpenStudy (xapproachesinfinity):

you could do \((3x ~~~~)(3x~~~~)\) since 3x times 3x is 9x^2

OpenStudy (xapproachesinfinity):

eh hold on my bad I'm not thinking straight! let's go with (3x )(3x ) case 2 and 5 multiply to 10 as i said above! if i have -2 and 5 the middle term will be -6x+15x=9x if it is 2 and -5 we will get for the middle term 6x-15x=-9x so -2 and 5 are good it would be \((3x+5)(3x-2)\)

OpenStudy (xapproachesinfinity):

what i did first in incorrect! i forgot that we are multiplying by 9x so the middle term would be 10x-9x=x but we want 9x not x so not a good choice

OpenStudy (anonymous):

ok, thanks you've helped a lot

OpenStudy (xapproachesinfinity):

welcome

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