A=x^3 + y^3 + 3xy(x+y)
  =x+3x^y+3xy^2+y^3
  =(x+y)^3=2^3=8
B=x^2+2xy+y^2+4
  =(x+y)^2+4=4+4=8

C=x^3+y^3+3xy(x+y)+7(x+y)

  =(x+y)^3+7(x+y)
  =2^3+7.2
  =8+14=22

Bài 2:

\(M=x^2-2xy+y^2=\left(x-y\right)^2=\left(-3\right)^2=9\)

\(N=x^2+y^2=\left(x-y\right)^2+2xy=9+2.10=29\)

\(P=x^3-3x^2y+3xy^2-y^3=\left(x-y\right)^3=\left(-3\right)^3=-27\)

\(Q=x^3-y^3=\left(x-y\right)^3+3xy\left(x-y\right)=\left(-3\right)^3+3.10.\left(-3\right)=-117\)

Bài 1:

a)  \(A=x^2+2xy+y^2=\left(x+y\right)^2=\left(-1\right)^2=1\)

b)  \(B=x^2+y^2=\left(x+y\right)^2-2xy=\left(-1\right)^2-2.\left(-12\right)=25\)

c)  \(C=x^3+3x^2y+3xy^2+y^3=\left(x+y\right)^3=\left(-1\right)^3=-1\)

d)  \(D=x^3+y^3=\left(x+y\right)^3-3xy\left(x+y\right)=\left(-1\right)^3-3.\left(-12\right).\left(-1\right)=-37\)

a) \(A=x\left(x+2\right)+y\left(y-2\right)-2xy+37\)

\(A=x^2+2x+y^2-2y-2xy+37\)

\(A=\left(x^2-2xy+y^2\right)+\left(2x-2y\right)+37\)

\(A=\left(x-y\right)^2+2\left(x-y\right)+37\)

\(A=\left(x-y\right)^2+2\left(x-y\right)+1+36\)

\(A=\left(x-y+1\right)^2+36\)

Thay x - y = 7 vào A

\(A=\left(7+1\right)^2+36\)

\(A=8^2+36\)

\(A=64+36\)

\(A=100\)

b) \(B=x^3+x^2-y^3+y^2+xy-3x^2y+3xy^2-3xy-9\)

\(B=\left(x^3-3x^2y+3xy^2-y^3\right)+\left(x^2+xy-3xy+y^2\right)-9\)

\(B=\left(x-y\right)^3+\left(x^2-2xy+y^2\right)-9\)

\(B=\left(x-y\right)^3+\left(x-y\right)^2-9\)

Thay x - y = 7 vào B

\(B=7^3+7^2-9\)

\(B=343+49-9\)

\(B=383\)

c) \(C=x^3-x^2-y^3-y^2-3xy\left(x-y\right)+2xy\)

\(C=\left[x^3-y^3-3xy\left(x-y\right)\right]-\left(x^2-2xy+y^2\right)\)

\(C=\left(x-y\right)^3-\left(x-y\right)^2\)

Thay x - y = 7 vào C

\(C=7^3-7^2\)

\(C=343-49\)

\(C=294\)

d) \(D=x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95\)

\(D=x^3+x^2-y^3+y^2+xy-3x^2y+3xy^2-3xy-95\)

\(D=\left(x^3-3x^2y+3xy^2-y^3\right)+\left(x^2-2xy+y^2\right)-95\)

\(D=\left(x-y\right)^3+\left(x-y\right)^2-95\)

Thay x - y = 7 vào D

\(D=7^3+7^2-95\)

\(D=343+49-95\)

\(D=297\)

a ) có \(x^2+y^2+4x-2xy+4y+2019=\left(x-y\right)^2+4\left(x-y\right)+2019=49+28+2019=2096\)

b) \(x^3-3xy\left(x-y\right)-y^3-x^2+2xy-y^2=\left(x-y\right)^3-\left(x-y\right)^2=343-49=294\)

c)\(x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)=x^3-y^3+x^2+y^2+xy-3x^2y+3xy^2-3xy=\left(x-y\right)^3+\left(x-y\right)^2=343+49=392\)

M = x³ - 3xy(x - y) - y³ - x² + 2xy - y²

= [x³ - 3xy(x - y) - y³] - (x² - 2xy + y²)

= (x - y)³ - (x - y)²

= 7³ - 7²

= 294

\(\left(x^3+3x^2y+3xy^2+y^3-z^3\right):\left(x+y-z\right)\\ =\left[\left(x+y\right)^3-z^3\right]:\left(x+y-z\right)\\ =\left(x+y-z\right)\left[\left(x+y\right)^2+z\left(x+y\right)+z^2\right]:\left(x+y-z\right)\\ =x^2+2xy+y^2+xz+yz+z^2\)

Vậy chọn A 

a. Có \(x+y=2\Rightarrow x^2+2xy+y^2=4\Rightarrow x^2+y^2=4-2.\left(-3\right)=10\)

\(x^4+y^4=\left(x^2\right)^2+\left(y^2\right)^2=\left(x^2+y^2\right)^2-2x^2y^2\)

\(=10^2-2.\left(-3\right)^2=82\)

b. Ta có \(x+y=1\Rightarrow x^2+y^2=1-2xy\)

 \(x^3+y^3+3xy=\left(x+y\right)\left(x^2-xy+y^2\right)+3xy\)

\(=1.\left(1-2xy-xy\right)+3xy=1\)

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