Question:

This is simple algebra, but i'm lost?

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"Find two numbers such that 4 times the first number minus 4 times the second number equals 24 and twice the first number times the second number equals 30'

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  1. 4x - 4y = 24

    2xy = 30

    Divide the first equation by 4:

    x - y = 6

    -> y = 6 + x

    Divide the second one by 2:

    xy = 15

    -> x(6+ x) = 15

    x^2 + 6x = 15

    Complete the square:

    x^2 + 6x + 9 = 24

    x + 3 = ±sqrt(24) = ±2 sqrt(6)

    x = -3 ± 2 sqrt(6)


  2. Let the numbers be A and B

    Equation 1:

    4A - 4B = 24

    Equation 2:

    2AB = 30

    Simplify the first equation:

    4(A - B) = 24

    A - B = 24/4

    A - B = 6

    Solve for A:

    A = B + 6

    Substitute into equation #2:

    2(B + 6) * B = 30

    2B(B + 6) = 30

    2B² + 12B = 30

    Get everything on one side:

    2B² + 12B - 30 = 0

    Divide both sides by 2:

    B² + 6B - 15 = 0

    This doesn't factor nicely so you would have to use the quadratic formula:

    B = 1.899 or B = -7.899

    A = 7.899 or A = -1.899

    Are you sure you copied it correctly?

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