If 7 times the square of an integer is added to 5 times the integer, the result is 2. Find the integ

Discussion in 'Calculator Requests' started by math_celebrity, Apr 3, 2019.

  1. math_celebrity

    math_celebrity Administrator Staff Member

    If 7 times the square of an integer is added to 5 times the integer, the result is 2. Find the integer.

    • Let the integer be "x".
    • Square the integer: x^2
    • 7 times the square: 7x^2
    • 5 times the integer: 5x
    • Add them together: 7x^2 + 5x
    • The result is means an equation, so we set 7x^2 + 5x equal to 2
    7x^2 + 5x = 2

    This is a quadratic equation. To get it into standard form, we subtract 2 from each side:
    7x^2 + 5x - 2 = 2 - 2
    7x^2 + 5x - 2 = 0

    Type this problem into our search engine, and we get two solutions:

    1. x = 2/7
    2. x= -1
    The problem asks for an integer, so our answer is x = -1.

    Let's check our work by plugging x = -1 into the quadratic:
    7x^2 + 5x - 2 = 0
    7(-1)^2 + 5(-1) - 2 ? 0
    7(1) - 5 - 2 ? 0
    0 = 0

    So we verified our answer, x = -1.
     

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