\(-\frac{1}{3}< \frac{1}{2}\)

\(-\frac{2}{6}< \frac{3}{6}\)

\(-\frac{2}{6}< \frac{-2}{7}< -\frac{1}{7}< \frac{1}{7}< \frac{2}{7}< \frac{3}{6}\)

\(\left(ab\right)\left(bc\right)\left(ac\right)=c.4a.9b\)

\(\left(abc\right)^2=36abc\)

+a=0 hoặc b=0; hoặc c=0

+ abc=36 => ab=c=> abc=c² =36=> c=6 hoac -6

                                         4a²=36 => a=3; -3

                                         9b²=36=> b=2;-2

vậy (a;b;c) thuộc (o;0;0);(3;2;6);(3;-2;-6);(-3;-2;6);(-3;2;-6)

vì   - |x-6| \(\le0\) và  - (xy-100)² \(\le0\)

=> M \(\le2016+0+0=2016\)

MaxM=2016 khi x=6 ; y=100/6=50/3

\(B=-\left(x^2+2x\left(y-1\right)+\left(y-1\right)^2\right)-\left(2y^2+2y-\left(y-1\right)^2\right)-15\)

\(=-\left(x+y-1\right)^2-\left(y+2\right)^2-10\le-10\)

Max B=-10 khi y=-2; x= 3

\(A=-\left(x^2-2x\left(y+1\right)+\left(y+1\right)^2\right)-\left(4y^2-10y-5-\left(y+1\right)^2\right)\)

\(=-\left(x-y-1\right)^2-\left(3y^2-12y-6\right)\)

\(=-\left(x-y-1\right)^2-3\left(y-2\right)^2+18\le18\)

Max A=18 khi y=2; x=3

B= -3 nhé

\(B=\left(x^2+x\left(y-3\right)+\frac{\left(y-3\right)^2}{4}\right)+\left(y^2-3y-\frac{\left(y-3\right)^2}{4}\right)\)

\(=\left(x+\frac{y-3}{2}\right)^2+\frac{3\left(y^2-2y+1\right)-12}{4}\)

\(=\left(....\right)^2+\frac{3}{4}\left(y-1\right)^2-3\ge3\)

Min B=-3 khi y=1;x=1