Absolutely

Algebra Level 2

Find the sum of the values of the solution set

2 x + x = 3 \frac { 2 }{ \left| x \right| } +\left| x \right| \quad =\quad 3

3 2 -1 1 0

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3 solutions

Hobart Pao
Nov 18, 2015

I let y = x y =\left| x \right| and solved the quadratic equation 0 = ( y 1 ) ( y 2 ) 0 = (y-1)(y-2) . That yields y = 1 , y = 2 y=1, y=2 . Substitute back: x = 1 x = ± 1 \left|x \right| = 1 \rightarrow x= \pm 1 and x = 2 x = ± 2 \left| x\right| = 2 \rightarrow x= \pm 2 .

Dhaval Furia
Jun 26, 2016

The given equation either has a solution or not.

In case it does not, then the sum of the values of the solution set is 0 0 .

In case it does, let it be x = a x = a

\Rightarrow 2 a + a = 3 \frac {2}{|a|} + |a| = 3

We can claim that x = a x = -a is also a solution, because

2 a + a = 2 a + a = 3 \frac {2}{|-a|} + |-a| = \frac {2}{|a|} + |a| = 3

Hence for every solution x = a x = a , there exists a solution x = a x = -a which gives the sum of the values of the solution set to be 0 0 , anyways.

There is no need to find the solutions, I think.

Kay Xspre
Nov 9, 2015

Multiplying with x |x| on both sides gives 2 + x 2 = 3 x 2+|x|^2=3|x| , or simply ( x 1 ) ( x 2 ) = 0 (|x|-1)(|x|-2) = 0 . From this equation, we get x = 2 , 1 , 1 , 2 x = -2, -1, 1, 2 , and the sum of possible values is zero.

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