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Mathematics 16 Online
OpenStudy (anonymous):

Factor completely.

OpenStudy (anonymous):

\[18x^3y-33x^2y^2-30xy^3\]

OpenStudy (anonymous):

is there something that we could factor out of this?

OpenStudy (anonymous):

maybe something that all the terms have in common?

OpenStudy (anonymous):

yes the xy and hmm i guess the number 3?

OpenStudy (anonymous):

very good, if we factor those out we will get: 3xy(6x^2-11xy-10y^2)

OpenStudy (anonymous):

now, we have to see if that quadratic onnthe inside can be factored, what do you think?

OpenStudy (anonymous):

hmmm im not sure i thought 2 but that is wrong.

OpenStudy (anonymous):

3xy(6x^2-11xy-10y^2) Well, we can use a bit of guess and check: lets say we start off with: (3x+?)(2x+?), since these two particular terms well give us 6x^2 okay

OpenStudy (anonymous):

ok got it so far

OpenStudy (anonymous):

Sorry, one of them has to have a minus sign,now (3x+?)(2x-?)=6x^2-3x?+2x?-?^2

OpenStudy (anonymous):

now, the reason i did all of that is because we need to find numbers that will give us what we want, namely 6x^2-11xy-10y^2

OpenStudy (anonymous):

So what we factor with has to have a minus sign?

OpenStudy (anonymous):

yes, because if you notice the orginal quadratic has :6x^2-11xy-10y^2, it has two minus signs. So we need a minus sign in one of our terms. Now let me as you what comnbination of number well give us -10y^2

OpenStudy (anonymous):

thats i to say, what numbers when ,multiplied together give us -10y^2

OpenStudy (anonymous):

hmmm -2 and 5? right?

OpenStudy (anonymous):

yes, in fact it s -2y and 5y, right, since we also want that y^2 part

OpenStudy (anonymous):

oh yeah sorry forgot that part.

OpenStudy (anonymous):

now we have (3x+?,)(2x-?), but we have found the numbers that should replace the quetion marks, can you postion those numbers so that we get: 6x^2-11xy-10y^2

OpenStudy (anonymous):

so wait is it 3x-2 and 2x+5?

OpenStudy (anonymous):

well, remeber we found the two numbers to be 2y and 5y

OpenStudy (anonymous):

oh yeah so 2y and 5y sorry haha

OpenStudy (anonymous):

so, now you are saying that it should be : (3x-2y) and (2x+5y), does, that when you multiply it our, give you 6x^2-11xy-10y^2

OpenStudy (anonymous):

i think so cause 3*2=6 and -2*5=-10 and how do you get the 11xy

OpenStudy (anonymous):

its from the two middle terms

OpenStudy (anonymous):

oh yeah forgot bout foil

OpenStudy (anonymous):

now, you have the correct terms. But just make sure you get the result you want.

OpenStudy (anonymous):

the answer should look something like this ?xy(?x+?y)(?x-?y)

OpenStudy (anonymous):

The answer, when completlely, factored looks like this: 3xy(2x-5y)(3x+3y)

OpenStudy (anonymous):

hmmm i got it wrong but i have 2 more tries i wonder what is wrong.

OpenStudy (anonymous):

I got it wrong.

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