Which equation of the solutions of x2 = -7x – 8

Question

Which equation of the solutions of x2 = -7x – 8

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Phúc Điền 4 years 2021-08-30T12:10:07+00:00 2 Answers 11 views 0

Answers ( )

  1. thanhcong
    0
    2021-08-30T12:11:19+00:00
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    Answer:

    x = \frac{- 7 + \sqrt{17}}{2} \ , \ x = \frac{-7 - \sqrt{17}}{2}

    Step-by-step explanation:

    x^2 = - 7x - 8\\\\x^2 + 7x + 8 = 0 \\\\

    x = \frac{- b \pm \sqrt{b^2 - 4ac}}{2a}\\\\               [ \ a = 1 , \ b = 7 , \ c = 8 \ ]

    x = \frac{-7 \pm \sqrt{49 - (4\times 8)}}{2} \\\\x = \frac{-7 \pm \sqrt{17}}{2} \\\\x = \frac{-7 + \sqrt{17}}{2} , \ , \frac{-7 - \sqrt{17}}{2}

  2. RobertKer
    0
    2021-08-30T12:11:49+00:00
    Reply

    Answer:

    x = 1, -5.56

    Step-by-step explanation:

    x^2 = -7x – 8

    shift -7x and -8 to the other side . Remember when u shift minus changes into plus.

    x^2 + 7x + 8 = 0

    using quadratic equation formula

    in quadratic equation one value comes positive and other comes in negative

    a = 1  , b = 7 and c = 8

    taking positive sign

    x = (-b + \sqrt{b^2 - 4*a*c}) /2*a

    x = (-7 + \sqrt{7^2 - 4*1*8} ) /2*1

    x = (-7 + \sqrt{49 + 32} ) /2

    x = (-7 + \sqrt{81} )/ 2

    x = -7 + 9 / 2

    x = 2/2

    x = 1

    taking negative sign

    (-b – \sqrt{b^2 - 4*a*c} ) /2*a

    x = (-7 – \sqrt{7^2 - 4*1*8} ) /2*1

    x = (-7 – \sqrt{49 - 32} ) /2

    x = -7 – \sqrt{17} / 2

    x = -7 – 4.12 / 2

    x = -11.12/2

    x = -5.56

    therefore x = 1 , – 5.56

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Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )