Question

tìm GTLN 

6-8x-x^2

Answer 1

\(=-\left(x^2+8x-6\right)\\ =-\left(x^2+2.4x+16-22\right)\\ =-\left(x+4\right)^2+22\le22\forall x\)

Dấu = xảy ra khi

\(x+4=0\\ x=-4\)

Vậy \(Min=22khix=-4\)