\(\Rightarrow Ax=x^2+25x+144\)
\(\Leftrightarrow x^2+\left(25-A\right)x+144=0\)
pt có nghiệm khi Δ\(\ge0\)
\(\Rightarrow\left(25-A\right)^2-4.144\ge0\)
\(\Leftrightarrow\left|25-A\right|\ge24\)
\(\Leftrightarrow\left[{}\begin{matrix}25-A\ge24\\25-A\le-24\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}A\le-1\\A\ge49\end{matrix}\right.\)
Vậy Amin=49\(\Leftrightarrow\frac{x^2+25x+144}{x}=49\)
\(\Rightarrow x^2+\left(25-49\right)x+144=0\)
\(\Leftrightarrow x^2-24x+144=0\)
\(\Leftrightarrow x=12\)
Vậy Amin=49\(\Leftrightarrow x=12\).
Đúng 0
Bình luận (0)
