True or false

Algebra Level 2

Is it true that x = x |x| =x for all real x x ?

True False

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3 solutions

Pham Khanh
Apr 22, 2016

For x = y |x|=y we have x = ± y x=\pm y So for x = x |x|=x we only have x = x x = x \begin{aligned} \ x & = & x \\x & =& -x \end{aligned} But obviously , x x x \neq -x So the answer is F a l s e \huge \boxed{False}

Hung Woei Neoh
Apr 23, 2016

The absolute value function x |x| can be defined as a piecewise function as below:

x = { x x 0 x x < 0 |x| = \begin{cases} x &\quad x \geq 0\\ -x &\quad x < 0 \end{cases}

From this definition, we can see clearly that x = x |x| = x only for all non-negative real x x .

Therefore, the statement given is False \boxed{\text{False}}

L e t Let

x = 2 x = -2

2 = 2 \left| -2 \right| =-2

2 2 \boxed{ 2\neq -2}

Actually you'll need to say that I s i t t r u e t h a t x = x x R Is~it~true~that~|x|=x~~\forall x \in \mathbb{R}

Pham Khanh - 5 years, 1 month ago

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Ok and thank you for the note

حسن العطية - 5 years, 1 month ago

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