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Math Help - Making x the subject (HARD)

  1. #1
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    Making x the subject (HARD)

    Don't get how you do this!

    I am sure you don't start working it out by multiplying the bracets but i dunno!

    here it is:

    5(x-3) = y(4-3x)

    Thanks a bubble
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  2. #2
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by Danielisew View Post
    Don't get how you do this!

    I am sure you don't start working it out by multiplying the bracets but i dunno!

    here it is:

    5(x-3) = y(4-3x)

    Thanks a bubble
    You are solving for x?
    5(x - 3) = y(4 - 3x)

    5x - 15 = 4y - 3xy<-- Distribute the parentheses

    5x + 3xy = 4y + 15<-- Get all x terms on one side

    (5 + 3y)x = 4y + 15<-- Factor the LHS

    x = \frac{4y + 15}{3y + 5}

    -Dan
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  3. #3
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Danielisew View Post
    Don't get how you do this!

    I am sure you don't start working it out by multiplying the bracets but i dunno!

    here it is:

    5(x-3) = y(4-3x)

    Thanks a bubble
    what did you try?

    5(x - 3) = y(4 - 3x) ...........expand

    \Rightarrow 5x - 15 = 4y - 3xy.....now get all the terms with x's on one side

    \Rightarrow 5x + 3xy = 4y + 15

    Can you take it from here?

    EDIT: Oh, well, Dan finished the problem already, forget it
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  4. #4
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    Thanks both of you..
    But how can you just get x by itself when you factorised it? Technically, isn't it still multiplying the bracets, so how did you just take it by itself and make it the subject of what was there ..

    Thanks
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  5. #5
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Danielisew View Post
    Thanks both of you..
    But how can you just get x by itself when you factorised it? Technically, isn't it still multiplying the bracets, so how did you just take it by itself and make it the subject of what was there ..

    Thanks
    maybe i'm answering the wrong question, but once you factor out the x, you just divide both sides by what is multiplying the x. this gets the x by itself

    This is my 2222 post! It's not a multiple of 100, but i think it looks cool nonetheless
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  6. #6
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    lol nice

    Thanks a lot
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