\(C=-\left(x^2+4x-2\right)=-\left(x^2+4x+4-6\right)=-\left(x+2\right)^2+6< =6\)
Dấu '=' xảy ra khi x=-2
\(C=2-4x-x^2\)
\(C=2-\left(x^2+4x\right)\)
\(C=2-\left(x^2+4x+4-4\right)\)
\(C=2-\left(x^2+4x+4\right)+4\)
\(C=-\left(x+2\right)^2+6\le6\)
Dấu "=" xảy ra khi \(x+2=0\)
\(\Leftrightarrow x=-2\)
Vậy \(Max_C=6\) khi \(x=-2\)
C = 2 - 4X - x2
C = -(x2 + 4X +4) +6
C = -(x+2)2 + 6
vì (x+2)2\(\ge\) 0 \(\Rightarrow\)- (x+2)2 \(\le\) 0 \(\Rightarrow\)C = -(2x+2)2 \(\le\) 6
c(max) = 6 dấu bằng xảy ra khi x = -2
