Question

Answer 1

`2009 - |x - 2009| = x `

`=> |x - 2009| = 2009 - x `

`=> x - 2009 = 2009 - x ` hoặc ` x - 2009 =x - 2009`

`=> 2x = 2009 . 2` hoặc `0x = 0`

`=> x = 2009` hoặc `x in R`

Vậy `x in R`

Answer 2

\(2009-\left|x-2009\right|=x\)

\(\Leftrightarrow\left|x-2009\right|=2009-x\)

\(\Leftrightarrow\left|x-2009\right|=-\left(x-2009\right)\)

\(\Leftrightarrow x-2009\le0\)

\(\Leftrightarrow x\le2009\)