-2<=x<=5

=>(x+2)(x-5)<=0

=>\(x^2-3x-10\le0\)

=>\(x^2\le3x+10\) (1)

-2<=y<=5

=>(y+2)(y-5)<=0

=>\(y^2-3y-10\le0\)

=>\(y^2\le3y+10\)

=>\(2y^2\le6y+20\) (2)

-2<=z<=5

=>(z+2)(z-5)<=0

=>\(z^2-3z-10\le0\)

=>\(z^2\le3z+10\)

=>\(3z^2\le9z+30\) (3)

Từ (1),(2),(3) suy ra M<=3x+10+6y+20+9z+30=3(x+2y+3z)+60=3*9+60=87

Dấu '=' xảy ra khi (x;y;z)∈{(-2;-2;5);(5;5;-2)}

C=(2x-1)(x-1)(2x^2-3x-1)+2017

=(2x^2-3x+1)(2x^2-3x-1)+2017

=(2x^2-3x)^2-1+2017

=(2x^2-3x)^2+2016>=2016

Dấu = xảy ra khi 2x^2-3x=0

=>x=0 hoặc x=3/2

D=(x-1)(x-6)(x-3)(x-4)+10

=(x^2-7x+6)(x^2-7x+12)+10

=(x^2-7x)^2+18*(x^2-7x)+72+10

=(x^2-7x+9)^2+1>=1

Dấu = xảy ra khi x^2-7x+9=0

=>\(x=\dfrac{7\pm\sqrt{13}}{2}\)

\(Taco:\)

\(|x^2-x+1|-|x^2-x-2|=|x^2-x+1|+\left(-|x^2-x-2|\right)\)

\(\ge|x^2-x+1-x^2+x+2|=3\)

Dấu "=" xảy ra khi: \(\left(x^2-x+1\right)\left(x^2-x-2\right)\ge0\Leftrightarrow........\)

P=x/x+1 + y/y+1 + z/z+1=x+1-1/x+1 + y+1-1/y+1 + z+1-1/z+1

=1 - 1/x+1 + 1 - 1/y+1 + 1 - 1/z+1

=3 - (1/x+1 + 1/y+1 + 1/z+1)

Áp dụng bđt cauchy- schwarz dạng engel:

1/x+1 + 1/y+1 + 1/z+1 = 1²/x+1 + 1²/y+1 + 1²/z+1 >/ (1+1+1)²/x+1+y+1+z+1 >/ 9/4 (do x+y+z=1)

=> P </ 3 - 9/4 = 3/4 

maxP=3/4 

\(P=3-\left(\frac{1}{x+1}+\frac{1}{y+1}+\frac{1}{z+1}\right)\le3-\frac{9}{x+y+z+3}=\frac{3}{4}\)

\(P=\left|x\right|+\left|y\right|+\left|z\right|\)

Không mất tính tổng quát giả sử \(x\le y\le z\).

Khi đó \(x\le0;z\ge0\).

+) Nếu \(y\geq 0\) thì \(P=z-x+y=z-x-x-z=-2x\le2\).

+) Nếu \(y< 0\) thì \(P=z-x-y=z-x+z+x=2z\le2\).

Tóm lại \(P\le2\). Đẳng thức xảy ra khi, chẳng hạn x = -1; y = 0; z = 1.

Vậy Max P = 2 khi x = -1; y = 0; z = 1.