Question

Tìm GTLN của:

-2x²-16x+34

Answer 1

\(-2x^2-16x+34=-2\left(x^2+8x+16\right)+66=-2\left(x+4\right)^2+66\le66\)

Dấu "=" xảy ra khi \(-2\left(x+4\right)^2=0\Rightarrow x=-4\)

Answer 2

A = -2x² - 16x + 34 = -2(x² + 8x - 17) = -2 [ (x + 4)² - 33 ] = -2(x + 4)² + 66  \(\le\)66  (vì -2(x+4)² \(\le\)0)

Max A = 66 \(\Leftrightarrow\)x + 4 = 0         \(\Leftrightarrow\)x = -4