Find the value of x x

Algebra Level 3

1 x 3 + 1 x 4 = 1 x 2 + 1 x 5 \large \dfrac1{x-3} + \dfrac1{x-4} = \dfrac1{x-2} + \dfrac1{x-5}

What is the value of x x satisfying the equation above?


The answer is 3.5.

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3 solutions

Hung Woei Neoh
May 30, 2016

1 x 3 + 1 x 4 = 1 x 2 + 1 x 5 x 4 + x 3 ( x 3 ) ( x 4 ) = x 5 + x 2 ( x 2 ) ( x 5 ) ( 2 x 7 ) ( x 2 ) ( x 5 ) = ( 2 x 7 ) ( x 3 ) ( x 4 ) ( 2 x 7 ) ( x 2 7 x + 10 ) ( 2 x 7 ) ( x 2 7 x + 12 ) = 0 ( 2 x 7 ) ( ( x 2 7 x + 10 ) ( x 2 7 x + 12 ) ) = 0 ( 2 x 7 ) ( 2 ) = 0 2 x 7 = 0 2 x = 7 x = 7 2 \dfrac{1}{x-3}+\dfrac{1}{x-4}=\dfrac{1}{x-2}+\dfrac{1}{x-5}\\ \dfrac{x-4+x-3}{(x-3)(x-4)} = \dfrac{x-5+x-2}{(x-2)(x-5)}\\ (2x-7)(x-2)(x-5) = (2x-7)(x-3)(x-4)\\ (2x-7)(x^2-7x+10) - (2x-7)(x^2-7x+12) = 0\\ (2x-7)\left((x^2-7x+10) - (x^2-7x+12)\right) = 0\\ (2x-7)(-2) = 0\\ 2x-7=0\\ 2x=7\\ x=\boxed{\dfrac{7}{2}}

Edwin Gray
Jul 20, 2018

Collecting terms, we have (2x -7)/[(x - 3)(x - 4)] = (2x -7)/{x _ 2)(x _ 5)]. The numerators are equal, the denominators are not. This can only happen if numerator = 0 = 2x -7, s- x = 3.5. Ed Gray

Abdullah Ahmed
May 29, 2016

1 x 3 \frac{1}{x-3} + 1 x 4 \frac{1}{x-4} = 1 x 2 \frac{1}{x-2} + 1 x 5 \frac{1}{x-5}

o r or , 1 x 3 \frac{1}{x-3} - 1 x 2 \frac{1}{x-2} = 1 x 5 \frac{1}{x-5} - 1 x 4 \frac{1}{x-4}

o r , or, x 3 x + 2 x 2 5 x + 6 \frac{x-3-x+2}{x^2-5x+6} = x 5 x + 4 x 2 9 x + 20 \frac{x-5-x+4}{x^2-9x+20}

o r , or, 5 x -5x + 6 6 = 9 x -9x + 20 20

S o So , x x = 7 2 \frac{7}{2}

You have made a mistake in 2nd line.

Adnan Roshid - 5 years ago

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is it ok now :)

Abdullah Ahmed - 5 years ago

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