Help with solving x by completing the square

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    4x2 + 8x - 1
    => 4 [ x2 + 2x ] - 1
    => 4 [ (x + 1) 2 - 1 ] - 1
    => 4 (x + 1) 2 - (8/32) - (4/4)
    => 4 (x + 1) 2 - (3/4)

    What's my next step from here?
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    (Original post by ℓove)
    4x2 + 8x - 1
    => 4 [ x2 + 2x ] - 1
    => 4 [ (x + 1) 2 - 1 ] - 1
    => 4 (x + 1) 2 - (8/32) - (4/4)
    => 4 (x - 1) 2 - (3/4)

    What's my next step from here?
    Two things;

    => 4 (x + 1) 2 - (8/32) - (4/4) - this line isnt correct, look at how you multiplied the bracket above this line through by 4

    => 4 (x - 1) 2 - (3/4) - here inside the bracket has changed from (x+1) to (x-1), maybe this is just a typo though.
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    (Original post by DylanJ42)
    Two things;

    => 4 (x + 1) 2 - (8/32) - (4/4) - this line isnt correct, look at how you multiplied the bracket above this line through by 4

    => 4 (x - 1) 2 - (3/4) - here inside the bracket has changed from (x+1) to (x-1), maybe this is just a typo though.
    Ohh it's -5/4, and yeah the other one was a typo.

    What do I do now?
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    (Original post by ℓove)
    Ohh it's -5/4, and yeah the other one was a typo.

    What do I do now?
    huh? are you meaning to write

     \displaystyle 4 \left((x - 1)^2 - \frac{5}{4}\right) ?

    if you wanted to write it without the big brackets it would be  \displaystyle 4(x - 1)^2 - 5

    After that youre done if youve just been asked to complete the sqaure

    Edit: oh solve for x, just difference of two squares from here -  \displaystyle a^2 - b^2 = (a+b)(a-b)
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    (Original post by DylanJ42)
    huh? are you meaning to write

     \displaystyle 4 \left((x - 1)^2 - \frac{5}{4}\right) ?

    if you wanted to write it without the big brackets it would be  \displaystyle 4(x - 1)^2 - 5

    After that youre done if youve just been asked to complete the sqaure

    Edit: oh solve for x, just difference of two squares from here -  \displaystyle a^2 - b^2 = (a+b)(a-b)
    Thanks I got it!!!
 
 
 
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