Question

Tìm GTLN của: D = -x² + 8x - 4

                          E = -2x² - 4x + 5

                          F = \(\frac{x^{2012}+2013}{x^{2012}+2011}\)

Answer 1

\(D=-x^2+8x-4\)

\(D=-x^2+8x-16+12\)

\(D=-\left(x-4\right)^2+12\)

Có \(-\left(x-4\right)^2\le0\)

\(\Rightarrow D\le12\)

Vậy Max D = 12<=>x=4

Answer 2

\(E=-2x^2-4x+5\)

\(E=-2x^2-4x-2+7\)

\(E=-2\left(x+1\right)^2+7\le7\)

Vậy Max E = 7<=>x=-1