Question

\(|\)X + 9 \(|\)+ \(|\)6-x \(|\) + 450

tìm GTNN cua bieu thuc

Answer 1

\(A=\left|x+9\right|+\left|6-x\right|+450\)

\(\left|x+9\right|\ge-x-9\)

\(\left|6-x\right|\ge x-6\)

\(\Rightarrow A\ge-x-9+x-6+45\)

\(\Rightarrow A\ge30\)

xét A = 30 khi 

\(\hept{\begin{cases}x+9< 0\\6-x< 0\end{cases}\Rightarrow\hept{\begin{cases}x< -9\\x>6\end{cases}\Rightarrow}voli}\)