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Mathematics

Solve the following equation by factorisation:

x3x+3+x+3x3=212\dfrac{x - 3}{x + 3} + \dfrac{x + 3}{x - 3} = 2\dfrac{1}{2}

Quadratic Equations

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Answer

Given,

x3x+3+x+3x3=212(x3)(x3)+(x+3)(x+3)(x+3)(x3)=52x23x3x+9+x2+3x+3x+9x2+3x3x9=52 x26x+9+x2+6x+9x29=522x2+18x29=522(2x2+18)=5(x29)4x2+36=5x2455x24x2=36+45x2=81x=81=±9.\phantom {\Rightarrow} \dfrac{x - 3}{x + 3} + \dfrac{x + 3}{x - 3} = 2\dfrac{1}{2} \\[1em] \Rightarrow \dfrac{(x - 3)(x - 3) + (x + 3)(x + 3)}{(x + 3)(x - 3)} = \dfrac{5}{2} \\[1em] \Rightarrow \dfrac{x^2 - 3x - 3x + 9 + x^2 + 3x + 3x + 9}{x^2 + 3x - 3x - 9} = \dfrac{5}{2} \\[1em]\ \Rightarrow \dfrac{x^2 - 6x + 9 + x^2 + 6x + 9}{x^2 - 9} = \dfrac{5}{2} \\[1em] \Rightarrow \dfrac{2x^2 + 18}{x^2 - 9} = \dfrac{5}{2} \\[1em] \Rightarrow 2(2x^2 + 18) = 5(x^2 - 9) \\[1em] \Rightarrow 4x^2 + 36 = 5x^2 - 45 \\[1em] \Rightarrow 5x^2 - 4x^2 = 36 + 45 \\[1em] \Rightarrow x^2 = 81 \\[1em] \Rightarrow x = \sqrt{81} = \pm 9.

Hence, value of x = +9 or -9.

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