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Mathematics

Solve the following equation using the formula :

2xx4+2x5x3=813\dfrac{2x}{x - 4} + \dfrac{2x - 5}{x - 3} = 8\dfrac{1}{3}

Quadratic Equations

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Answer

Given,

2xx4+2x5x3=8132x(x3)+(2x5)(x4)(x4)(x3)=2532x26x+2x28x5x+20x23x4x+12=2534x219x+20x27x+12=2533(4x219x+20)=25(x27x+12)12x257x+60=25x2175x+30025x212x2175x+57x+30060=013x2118x+240=0\Rightarrow \dfrac{2x}{x - 4} + \dfrac{2x - 5}{x - 3} = 8\dfrac{1}{3} \\[1em] \Rightarrow \dfrac{2x(x - 3) + (2x - 5)(x - 4)}{(x - 4)(x - 3)} = \dfrac{25}{3} \\[1em] \Rightarrow \dfrac{2x^2 - 6x + 2x^2 - 8x - 5x + 20}{x^2 - 3x - 4x + 12} = \dfrac{25}{3} \\[1em] \Rightarrow \dfrac{4x^2 - 19x + 20}{x^2 - 7x + 12} = \dfrac{25}{3} \\[1em] \Rightarrow 3(4x^2 - 19x + 20) = 25(x^2 - 7x + 12) \\[1em] \Rightarrow 12x^2 - 57x + 60 = 25x^2 - 175x + 300 \\[1em] \Rightarrow 25x^2 - 12x^2 - 175x + 57x + 300 - 60 = 0 \\[1em] \Rightarrow 13x^2 - 118x + 240 = 0

Comparing 13x2118x+240=013x^2 - 118x + 240 = 0 with ax2 + bx + c = 0 we get,

a=13,b=118,c=240.a = 13, b = -118, c = 240.

We know that,

x = b±b24ac2a\dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Substituting values we get,

x=(118)±(118)24(13)(240)2(13)=118±139241248026=118±144426=118±3826=118+3826 or 1183826=15626 or 8026=6 or 3113.\Rightarrow x = \dfrac{-(-118) \pm \sqrt{(-118)^2 - 4(13)(240)}}{2(13)} \\[1em] = \dfrac{118 \pm \sqrt{13924 - 12480}}{26} \\[1em] = \dfrac{118 \pm \sqrt{1444}}{26} \\[1em] = \dfrac{118 \pm 38}{26} \\[1em] = \dfrac{118 + 38}{26} \text{ or } \dfrac{118 - 38}{26} \\[1em] = \dfrac{156}{26} \text{ or } \dfrac{80}{26} \\[1em] = 6 \text{ or } 3\dfrac{1}{13}.

Hence, x = 6,3113.6, 3\dfrac{1}{13}.

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