difference between 2 positive numbers is 3 and the sum of their squares is 117

Discussion in 'Calculator Requests' started by math_celebrity, Oct 28, 2021.

  1. math_celebrity

    math_celebrity Administrator Staff Member

    difference between 2 positive numbers is 3 and the sum of their squares is 117

    Declare variables for each of the two numbers:
    • Let the first variable be x
    • Let the second variable be y
    We're given 2 equations:
    1. x - y = 3
    2. x^2 + y^2 = 117
    Rewrite equation (1) in terms of x by adding y to each side:
    1. x = y + 3
    2. x^2 + y^2 = 117
    Substitute equation (1) into equation (2) for x:
    (y + 3)^2 + y^2 = 117

    Evaluate and simplify:
    y^2 + 3y + 3y + 9 + y^2 = 117

    Combine like terms:
    2y^2 + 6y + 9 = 117

    Subtract 117 from each side:
    2y^2 + 6y + 9 - 117 = 117 - 117
    2y^2 + 6y - 108 = 0

    This is a quadratic equation:

    Solve the quadratic equation 2y2+6y-108 = 0

    With the standard form of ax2 + bx + c, we have our a, b, and c values:
    a = 2, b = 6, c = -108

    Solve the quadratic equation 2y^2 + 6y - 108 = 0

    The quadratic formula is denoted below:
    y = -b ± sqrt(b^2 - 4ac)/2a

    Step 1 - calculate negative b:
    -b = -(6)
    -b = -6

    Step 2 - calculate the discriminant Δ:
    Δ = b2 - 4ac:
    Δ = 62 - 4 x 2 x -108
    Δ = 36 - -864
    Δ = 900 <--- Discriminant
    Since Δ is greater than zero, we can expect two real and unequal roots.

    Step 3 - take the square root of the discriminant Δ:
    √Δ = √(900)
    √Δ = 30

    Step 4 - find numerator 1 which is -b + the square root of the Discriminant:
    Numerator 1 = -b + √Δ
    Numerator 1 = -6 + 30
    Numerator 1 = 24

    Step 5 - find numerator 2 which is -b - the square root of the Discriminant:
    Numerator 2 = -b - √Δ
    Numerator 2 = -6 - 30
    Numerator 2 = -36

    Step 6 - calculate your denominator which is 2a:
    Denominator = 2 * a
    Denominator = 2 * 2
    Denominator = 4

    Step 7 - you have everything you need to solve. Find solutions:
    Solution 1 = Numerator 1/Denominator
    Solution 1 = 24/4
    Solution 1 = 6

    Solution 2 = Numerator 2/Denominator
    Solution 2 = -36/4
    Solution 2 = -9

    As a solution set, our answers would be:
    (Solution 1, Solution 2) = (6, -9)

    Since one of the solutions is not positive and the problem asks for 2 positive number, this problem has no solution
     

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