bn lập bảng xét dấu rồi xét 4 khoảng nhé!!

Ta có: \( \left|x-2015\right|=\left|2015-x\right|\)

Ta lại có: \(\left|2015-x\right|+\left|x-2017\right|\ge\left|2015-x+x-2017\right|=2\)

        \(\Rightarrow P\ge\left|2016-x\right|+2\)

    Vì \(\left|2016-x\right|\ge0\)\(\Rightarrow\left|2016-x\right|+2\ge2\)

                     \(\Rightarrow P\ge2\)

       Khi đó: \(\left|2016-x\right|=0\)\(\Rightarrow2016-x=0\)\(\Rightarrow x=2016\)

             Vậy \(P_{min}=2\)\(\Leftrightarrow\)\(x=2016\)

Buề

Giải:

Ta có: \(P=\left|x-2015\right|+\left|2016-x\right|+\left|x-2017\right|\)

Vì \(\left\{{}\begin{matrix}\left|x-2015\right|\ge0\\\left|2016-x\right|\ge2016-x\\\left|x-2017\right|\ge x-2017\end{matrix}\right.\)

Nên \(P\ge2016-x+x-2017\)

\(P\ge-1\)

Vậy GTNN của P là -1

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Vì \(\left|x-7\right|\ge0;\left|x-2016\right|\ge0;\left|x-2017\right|\ge0\)

         Suy ra:\(\left|x-7\right|+\left|x+2016\right|+\left|x-2017\right|\ge0\)

      Dấu = xảy ra khi x-7=0;x=7

                                 x+2016=0;x=-2016

                                 x-2017=0;x=2017

Vậy Min A=0 khi x=7;-2016;2017

A = |x-7|+|x-2016|+|x-2017|

= |x-7|+|x-2016|+|2017-x|

≥ |x-7+2017-x|+|x-2016| = 2017+|x-2016|≥2017

để A nhỏ nhất => A = 2017

=> |x - 2016| = 0 => x = 2016

\(P=\left|x-2015\right|+\left|2016-x\right|+\left|2017-x\right|\)

\(\ge x-2015+0+2017-x=2\)

Dấu "=' xảy ra \(\Leftrightarrow\hept{\begin{cases}x-2015\ge0\\2016-x=0\\2017-x\ge0\end{cases}}\Leftrightarrow x=2016\)

Vậy ..

\(P=\left|x-2015\right|+\left|x-2016\right|+\left|x-2017\right|\)

    \(=\left(\left|x-2015\right|+\left|x-2017\right|\right)+\left|x-2016\right|\)

     \(=\left(\left|x-2015\right|+\left|2017-x\right|\right)+\left|x-2016\right|\)

      \(=\left|x-2015+2017-x\right|+\left|x-2016\right|\)

       \(=2+ \left|x-2016\right|\)

Vì \(\left|x-2016\right|\ge0\left(\forall x\in Z\right)\Rightarrow2+\left|x-2016\right|\ge2\)

Dấu "=" xảy ra khi (x-2015).(2017-x) >= 0 và x - 2016 = 0

                                                              <=> x = 2016

Vậy P_min = 2 khi x = 2016

mk ko viết lại đề

P= |x-2015|+|x-2016|+|2017-x|

\(\ge\)\(\left|x-2105+2017-x\right|+\left|x-2016\right|\) 

=\(\left|2\right|+\left|x-2016\right|=2+\left|x-2016\right|\)

Do |x-2016|\(\ge0\)=> \(2+\left|x-2016\right|\ge2\)

dấu "=" xảy ra khi (x-2015).(2017-x)\(\ge0\)

\(\Leftrightarrow\hept{\begin{cases}x\ge2015\\x\le2017\end{cases}\Rightarrow2015\le x\le2017}\)

Vậy GTNN của P=2  \(\Leftrightarrow2015\le x\le2017\)

Ta có:

A=|x−2016|+2017|x−2016|+2018 =|x−2016|+2018−1|x−2016|+2018 =1−1|x−2016|+2018 

Vì |x−2016|≥0⇒|x−2016|+2018≥2018⇒1|x−2016|+2018 ≤12018 

=>A=1−1|x−2016|+2018 ≥20172018 

=>A_min=20172018 <=>|x-2016|=0<=>x-2016=0<=>x=2016

A=|x-2017|+|x+2018|