Completing the square?

Your supposed to solve for x by completing the square. 3x^2+24x+36<0.

thanks.

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  • David
    Lv 7
    9 years ago
    Favorite Answer

    3x^2 + 24x < -36

    x^2 + 8x < -12

    x^2 + 8x + (8/2)^2 < -12 + (8/2)^2

    x^2 + 8x + 16 < 4

    (x + 4)^2 < 4

    x + 4 < ± √4

    x + 4 < ± 2

    x < -2

    x > -6

  • 9 years ago

    divide everything by 3.

    x^2+8x+12<0

    b/2 = 8/2=4

    (b/2)^2=16

    (x+4)^2<4

    x+4<2 or x+4<-2

    x<-2 or x<-6

  • Anonymous
    9 years ago

    3(x+4)^2 + 36 < 0 + 42

    3(x+4)^2 < 6

    (x+4)^2 < 2

    -5.4 < x < -2.6

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