A=2y^3-4y^2-28y+294

\(A=x^3-y^3-21xy\)

\(A=\left(x-y\right).\left(x^2+xy+y^2\right)-21xy\)

\(A=7.\left(x^2+xy+y^2\right)-21xy\)

\(A=7.\left(x^2+xy+y^2+3xy\right)\)

\(A=7.\left(x^2+2xy+y^2+2xy\right)\)

\(A=7.\text{[}\left(x+y\right)^2+2xy\text{]}\)

\(A=7.\left(7^2+2xy\right)\)

\(A=7^3+14xy\)

Ngáo rồi @@

\(\)

\(A=x^3-y^3-21xy\)

\(\Rightarrow A=\left(x-y\right)\left(x^2+xy+y^2\right)-21xy\)

\(\Rightarrow A=7\left(x^2+xy+y^2\right)-21xy\)

\(\Rightarrow A=7\left(x^2+xy+y^2-3xy\right)\)

\(\Rightarrow A=7\left(x^2+y^2-2xy\right)\)

\(\Rightarrow A=7\left(x-y\right)^2\)

\(\Rightarrow A=7.7^2\)

\(\Rightarrow A=7.49\)

\(\Rightarrow A=343\)

ak trách j :V lộn dấu :V 

a: \(=x^2+2x+y^2-2y-2xy+37\)

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

\(=7^2+2\cdot7+37=49+14+37=100\)

b: \(=x^3+x^2-y^3+y^2+xy-3xy\cdot\left(7+1\right)-95\)

\(=\left(x^3-y^3\right)+\left(x^2+y^2\right)+xy-24xy-95\)

\(=\left(x-y\right)^3+3xy\left(x-y\right)+\left(x-y\right)^2+2xy-23xy-95\)

\(=7^3+3xy\cdot7+49-21xy-95\)

\(=343+49-95=297\)

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

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

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

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

\(=7^2+2.7+34\)

\(=100\)

b) \(x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95\)

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

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

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

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

\(=297\)

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

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

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

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

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

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

\(A=8^2+36\)

\(A=100\)

\(B=x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95\) \((9^5\) \(sai\)\()\)

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

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

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

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

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

\(B=297\)