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Math Help - Factoring! YUCK!

  1. #1
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    Factoring! YUCK!

    1.) 36x+18xy-9y-18
    2.) 4-36x^2
    3.) 42x^2-24
    4.) 12x^2-5xy-3y^2
    5.) -14r^2-11rs+15s^2
    6.) x^4-x^2-30

    I'm really struggling with this so any help would be greatly appreciated!
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by epetrik View Post
    1.) 36x+18xy-9y-18
    factor by grouping. there is a common 18x in the first two terms, and a common -9 in the last two

    2.) 4-36x^2
    write as 2^2 - (6x)^2

    now apply the formula for the difference of two squares factorization

    3.) 42x^2-24
    begin by factoring out the common 6

    now, what do you aee?

    4.) 12x^2-5xy-3y^2
    these are one of those two-way quadratic thingys.

    here's a tip: forget the y for a while and treat it as 12x^2 - 5x - 3 and factor that. when finished, attach a y to the constant terms, and that will take care of the y's in your expression

    5.) -14r^2-11rs+15s^2
    same advice as the last problem

    6.) x^4-x^2-30
    treat this as (x^2)^2 - (x^2) - 30

    this is a quadratic in x^2, factor it as you would a quadratic. but instead of x you are using x^2

    if it is hard for you to visualize, let y = x^2, then you have y^2 - y - 30. factorize this, and then replace all the y's with x^2's
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  3. #3
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    STILL trying to factor!

    I totally appreciate the previous help...but I still don't get number 2, 4,5,6
    HELP!!!!

    Quote Originally Posted by Jhevon View Post
    factor by grouping. there is a common 18x in the first two terms, and a common -9 in the last two

    write as 2^2 - (6x)^2

    now apply the formula for the difference of two squares factorization

    begin by factoring out the common 6

    now, what do you aee?

    these are one of those two-way quadratic thingys.

    here's a tip: forget the y for a while and treat it as 12x^2 - 5x - 3 and factor that. when finished, attach a y to the constant terms, and that will take care of the y's in your expression

    same advice as the last problem

    treat this as (x^2)^2 - (x^2) - 30

    this is a quadratic in x^2, factor it as you would a quadratic. but instead of x you are using x^2

    if it is hard for you to visualize, let y = x^2, then you have y^2 - y - 30. factorize this, and then replace all the y's with x^2's
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by epetrik View Post
    I totally appreciate the previous help...but I still don't get number 2, 4,5,6
    HELP!!!!
    for 2, recall that a^2 - b^2 = (a + b)(a - b)

    what is your a and b in #2?

    as for the others, can you factorize the ones i gave? namely, 12x^2 - 5x - 3 (you can use the AC-method, please tell me you know what that is ) and y^2 - y - 30 (remember how to deal with these guys? think of two numbers that you can multiply to get -30 (the constant term) and add to get -1 (the coefficient of y) then put them in the positions of the *'s as in (y + *)(y + *))
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  5. #5
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    THANK YOU THANK YOU THANK YOU!!!!!!!
    I totally forgot about the AC Method!
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