Question

Tìm min;max                                                     E=2x² -8x+7

F=x²+ x +1

 

Answer 1

 * \(F=x^2+x+1=x^2+x+\frac{1}{4}+\frac{3}{4}\)

\(\Rightarrow F=\left(x+\frac{1}{2}\right)^2+\frac{3}{4}\ge\frac{3}{4}\)

Vậy \(minF=\frac{3}{4}\Leftrightarrow x=-\frac{1}{2}\)

Answer 2

\(E=2x^2-8x+7=2x^2-8x+8-1=2\left(x-2\right)^2-1\ge-1.\)

Emin = -1 khi x = 2