the equation x^2 + y^2 + 21 = 40 + 18y. What is the radius of this cookie?​

Question

the equation x^2 + y^2 + 21 = 40 + 18y. What is the radius of this cookie?​

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Thu Cúc 3 years 2021-08-14T17:41:40+00:00 1 Answers 6 views 0

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  1. ThanhThu
    0
    2021-08-14T17:43:20+00:00
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    Answer:

    The radius is 10

    Step-by-step explanation:

    Given

    x^2 + y^2 + 21 = 40 + 18y.

    Required

    The radius

    Rewrite as:

    x^2 + y^2 - 18y = 40-21

    Subtract 81 from both sides

    x^2 + y^2 - 18y +81= 40-21+81

    Expand

    x^2 + y^2 - 9y - 9y +81= 40-21+81

    Factorize

    x^2 + y( y- 9) - 9(y -9)= 40-21+81

    Factor out y – 9

    x^2 + (y- 9) (y -9)= 40-21+81

    Express as squares

    x^2 + (y- 9)^2= 100

    x^2 + (y- 9)= 10^2

    The equation of a circle is:

    (x - a)^2 + (y- b)= r^2

    By comparison:

    r^2=10^2

    r = 10

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