Áp dụng BDT \(\left|a\right|+\left|b\right|\ge\left|a+b\right|\) ta có:
\(A=\left|x-136\right|+\left|x-36\right|\)
\(=\left|x-136\right|+\left|36-x\right|\)
\(\ge\left|x-136+36-x\right|=100\)
Dấu "=" xảy ra khi \(36\le x\le136\)
Vậy \(Min_A=100\) khi \(36\le x\le136\)