When 4 times a positive number is subtracted from the square of the number, the result is 5. Find the number.

Question

When 4 times a positive number is subtracted from the square of the number, the result is 5. Find the number.

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Nho 3 years 2021-07-26T11:59:22+00:00 1 Answers 21 views 0

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  1. minhkhang
    0
    2021-07-26T12:01:20+00:00
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    Answer:

    5

    Step-by-step explanation:

    x² – 4x = 5

    x² – 4x – 5 = 0

    the solution of a quadratic equation is

    x = (-b ± sqrt(b² – 4ac))/(2a)

    a = 1

    b = -4

    c = -5

    x = (4 ± sqrt(16 + 20))/2 = (4 ± sqrt(36))/2

    x1 = (4 + 6)/2 = 5

    x2 = (4 – 6)/2 = -1

    since we are looking only for a positive number, x=5 is the answer.

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