a=2/9 b=11/9. trung bình cộng=13/18.

giúp đi  mn  HELP ME PLSSSSSSSSSSSSSSSSSSSSSS

a, Thay x = 2 ; y = -1 ta đc 

\(A=\left(2-2\right)^2-2-2=-4\)

b, \(\left(x^2+4>0\right)\left(x-1\right)=0\Leftrightarrow x=1\)Thay vào ta đc

\(B=3+8-1=10\)

c, Thay x = 1 ; y = -1 ta đc \(C=3,2.1.\left(-1\right)=-3,2\)

d, Thay vào ta đc \(D=3.3-5\left(-1\right)=9+5=14\)

Thay x = 1 ; y = -1 ta đc

\(\dfrac{1}{2}.1\left(-1\right)-\dfrac{3}{4}.1\left(-1\right)+1\left(-1\right)=-\dfrac{1}{2}+\dfrac{3}{4}-1=\dfrac{1}{4}-1=-\dfrac{3}{4}\)

`Answer:`

`16x^2y^5-2x^2y^5`

`=(16-2)x^2y^5`

`=14x^2y^5`

Thay `x=0,5` và `y=-1` vào biểu thức ta được: 

`14.0,5^2.(-1)^5`

`=3,5.(-1)`

`=-3,5`

\(6m=5n\Rightarrow m=\dfrac{5n}{6}\)

\(\Rightarrow P=\dfrac{4m-2n}{2m+5n}=\dfrac{4.\dfrac{5n}{6}-2n}{2.\dfrac{5n}{6}+5n}=\dfrac{\dfrac{4}{3}n}{\dfrac{20}{3}n}=\dfrac{\dfrac{4}{3}}{\dfrac{20}{3}}=\dfrac{4}{20}=\dfrac{1}{5}\)

@Nguyễn Việt Lâm Cảm ơn bạn nhiều nhe🥰🥰🥰.

\(M.N=2x^3y^3z.\dfrac{1}{2}x^3y^3z=\left(2.\dfrac{1}{2}\right)\left(x^3.x^3\right)\left(y^3.y^3\right)\left(z.z\right)=x^6y^6z^2\)

M x N = 2x³ . y³z . \(\dfrac{1}{2}\)x³ y³ z

= (x³ . x) . (y³ . y³) . (z . z) . \(\left(2.\dfrac{1}{2}\right)\)

= 1. x⁴ . y⁹ . z² 

= x⁴y⁹z²

\(A=2x^2-4x^3+7-x^2-3x^3\\ =\left(2x^2-x^2\right)-\left(4x^3+3x^3\right)+7\\ =x^2-7x^3+7\)

999999999999999999 x 9999999999

\(B=4x-7y+9x+3y+8-2^3\\ =\left(4x+9x\right)-\left(7y-3y\right)+\left(8-8\right)\\ =13x-4y\)

= 13x - 4y