Question

Tìm GTNN hoặc GTLN của

A=5-6x-2x^2

Answer 1

\(A=5-2\left(x^2+3x\right)=\frac{19}{2}-2\left(x^2+2.\frac{3}{2}x+\frac{9}{4}\right)\)

\(A=\frac{19}{2}-2\left(x+\frac{3}{2}\right)^2\le\frac{19}{2}\)

\(\Rightarrow A_{max}=\frac{19}{2}\) khi \(x=-\frac{3}{2}\)