Question

rút gọn biểu thức

|x +7,2| - | x -1,2|

Answer 1

|x+7,2|-|x-1,2|\(̸\)\(\le\)|x+7,2-x+1,2|=|8,4|=8,4

Dấu " = " xảy ra\(\Leftrightarrow\)(x+7,2)(x-1,2)

\(\Leftrightarrow\)\(\left\{{}\begin{matrix}\left\{{}\begin{matrix}x\le-7,2\\x\ge1,2\end{matrix}\right.\\-7,2\le x\le1,2\left(TM\right)\end{matrix}\right.\left(KTM\right)\)

Vậy |x+7,2|-|x-1,2|=8,4 \(\Leftrightarrow\)-7,2\(\le x\le\)1,2

Answer 2

TH1: x<-7,2

A=-x-7,2-(1,2-x)=-x-7,2-1,2+x=-8,4

TH2: -7,2<=x<1,2

A=x+7,2-(1,2-x)=x+7,2-1,2+x=2x+6

TH3: x>=1,2

A=x+7,2-x+1,2=8,4