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Math Help - Solve for x

  1. #1
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    Solve for x- REALLY REALLY URGENT

    y= 3(2x + 1)^2 - 5. Please show all working out >.<
    Last edited by delicate_tears; April 13th 2008 at 04:24 AM.
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  2. #2
    Moo
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    Hello,

    Why don't you try a little on your own ?

    And what exactly d'you want ? Solve for y=0 ? Or express x with y ?
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  3. #3
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    Quote Originally Posted by Moo View Post
    Hello,

    Why don't you try a little on your own ?

    And what exactly d'you want ? Solve for y=0 ? Or express x with y ?

    I wanted to solve for x, hence the topic. I tried it before , but I got (-1 + square root 15) /2, which was totally not the answer. That's why I wanted the steps, to show me how to get there. I know the answer, it's 0.145... and -1.145... I just need to know how to get round it.
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  4. #4
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    Quote Originally Posted by delicate_tears View Post
    y= 3(2x + 1)^2 - 5. Please show all working out >.<
    y = 3(2x + 1)^2 - 5

    y + 5 = 3(2x + 1)^2

    \frac{y + 5}{3} = (2x + 1)^2

    \sqrt{ \frac{y + 5}{3} } = 2x + 1

    \sqrt{ \frac{y + 5}{3} } - 1 = 2x

    \frac{ \sqrt{ \frac{y + 5}{3} } - 1 }{2} = x
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  5. #5
    Moo
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    You want to solve for x in 3(2x + 1)^2 - 5=0

    This is completely different than your previous question ^^

    Well

    3(2x+1)=5

    (2x+1)=5/3

    2x+1=sqrt(5/3) or -sqrt(5/3) remember this ! (a)=(-a)=a

    2x=-1+sqrt(5/3) or -1-sqrt(5/3)

    And then divide by 2.
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  6. #6
    Moo
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    Quote Originally Posted by janvdl View Post

    \sqrt{ \frac{y + 5}{3} } = 2x + 1
    OR

    -\sqrt{ \frac{y + 5}{3} } = 2x + 1

    Don't forget it
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