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Solve the equation 3sqrt(4x−3) − sqrt(5x+1) = 5 for integer values of x.

Mathematics

ScanSolve AI Answer

Answer

x=3x=3

Step-by-step solution

8 steps
  1. Determine the domain of the variables.

    For the square roots to be defined, the expressions under them must be non-negative:

    4x−3≥0  ⟹  4x≥3  ⟹  x≥344x-3 \ge 0 \implies 4x \ge 3 \implies x \ge \frac{3}{4} 5x+1≥0  ⟹  5x≥−1  ⟹  x≥−155x+1 \ge 0 \implies 5x \ge -1 \implies x \ge -\frac{1}{5}

    Combining these conditions, we must have x≥34x \ge \frac{3}{4}. Since xx is specified as an integer, xx must be 1,2,3,…1, 2, 3, \dots.

  2. Isolate one of the radical terms.

    The given equation is 34x−3−5x+1=53\sqrt{4x-3} - \sqrt{5x+1} = 5.
    Move the second radical term to the right side of the equation:

    34x−3=5+5x+13\sqrt{4x-3} = 5 + \sqrt{5x+1}
  3. Square both sides of the equation.

    (34x−3)2=(5+5x+1)2(3\sqrt{4x-3})^2 = (5 + \sqrt{5x+1})^2 9(4x−3)=52+2(5)5x+1+(5x+1)29(4x-3) = 5^2 + 2(5)\sqrt{5x+1} + (\sqrt{5x+1})^2 36x−27=25+105x+1+5x+136x - 27 = 25 + 10\sqrt{5x+1} + 5x+1 36x−27=26+5x+105x+136x - 27 = 26 + 5x + 10\sqrt{5x+1}
  4. Isolate the remaining radical term.

    Subtract 26 and 5x5x from both sides:

    36x−5x−27−26=105x+136x - 5x - 27 - 26 = 10\sqrt{5x+1} 31x−53=105x+131x - 53 = 10\sqrt{5x+1}
  5. Square both sides again.

    (31x−53)2=(105x+1)2(31x - 53)^2 = (10\sqrt{5x+1})^2 (31x)2−2(31x)(53)+532=100(5x+1)(31x)^2 - 2(31x)(53) + 53^2 = 100(5x+1) 961x2−3286x+2809=500x+100961x^2 - 3286x + 2809 = 500x + 100
  6. Rearrange the equation into a standard quadratic form ax2+bx+c=0ax^2+bx+c=0.

    961x2−3286x−500x+2809−100=0961x^2 - 3286x - 500x + 2809 - 100 = 0 961x2−3786x+2709=0961x^2 - 3786x + 2709 = 0
  7. Solve the quadratic equation for xx.

    Using the quadratic formula x=−b±b2−4ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}:

    x=−(−3786)±(−3786)2−4(961)(2709)2(961)x = \frac{-(-3786) \pm \sqrt{(-3786)^2 - 4(961)(2709)}}{2(961)} x=3786±14333796−104133961922x = \frac{3786 \pm \sqrt{14333796 - 10413396}}{1922} x=3786±39204001922x = \frac{3786 \pm \sqrt{3920400}}{1922}

    Calculate the square root: 3920400=1980\sqrt{3920400} = 1980.

    x=3786±19801922x = \frac{3786 \pm 1980}{1922}

    This gives two possible solutions:

    x1=3786+19801922=57661922=3x_1 = \frac{3786 + 1980}{1922} = \frac{5766}{1922} = 3 x2=3786−19801922=18061922=903961x_2 = \frac{3786 - 1980}{1922} = \frac{1806}{1922} = \frac{903}{961}
  8. Check the solutions against the domain and the original equation.

    We established that xx must be an integer and x≥34x \ge \frac{3}{4}.
    For x1=3x_1 = 3: This is an integer and 3≥343 \ge \frac{3}{4}.
    Substitute x=3x=3 into the original equation:
    34(3)−3−5(3)+1=312−3−15+13\sqrt{4(3)-3} - \sqrt{5(3)+1} = 3\sqrt{12-3} - \sqrt{15+1}
    =39−16= 3\sqrt{9} - \sqrt{16}
    =3(3)−4= 3(3) - 4
    =9−4=5= 9 - 4 = 5
    This matches the right side of the equation, so x=3x=3 is a valid solution.

    For x2=903961x_2 = \frac{903}{961}: This is not an integer, so it is not a valid solution according to the problem's condition that xx is an integer.

    The only integer solution is x=3x=3.

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