2 numbers that add up makes 5 but multiplied makes -36

Discussion in 'Calculator Requests' started by math_celebrity, Jul 7, 2020.

  1. math_celebrity

    math_celebrity Administrator Staff Member

    2 numbers that add up makes 5 but multiplied makes -36

    Let the first number be x and the second number be y. We're given two equations:
    1. x + y = 5
    2. xy = -36
    Rearrange equation (1) by subtracting y from each side:
    1. x = 5 - y
    2. xy = -36
    Substitute equation (1) for x into equation (2):
    (5 - y)y = -36
    5y - y^2 = -36

    Add 36 to each side:
    -y^2 + 5y + 36 = 0

    We have a quadratic equation. To solve this, we type it in our search engine and solve to get:
    y = (-4, 9)

    We check our work for each equation:
    1. -4 + 9 = -5
    2. -4(9) = -36
    They both check out
     

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