\(a,A=\left(2x+y\right)^2-\left(2x-y\right)^2\\ =\left(2x+y-2x+y\right)\left(2x+y+2x-y\right)\\ =2y\cdot4x\\ =8xy\\ b,B=\left(x-2y\right)^2-4y\left(x-2y\right)+4y^2\\ =x^2-4xy+4y^2-4xy+8y^2+4y^2\\ =x^2+16y^2-8xy\\ =\left(x-4y\right)^2\)

a) A = [(2x + y) - (2x - y)] . [(2x +y) + (2x - y)]

b) B = [(x - 2y) - 2y]²

Ta có:

B) Ta có: 2x-2y-x²+2xy-y²

⇔ 2(x-y)-(x²-2xy+y²)

⇔ 2(x-y)-(x-y)²

⇔ (x-y)(2-x+y)

Đúng thì tick nhé

câu a đâu

a: \(A=\left(a+b\right)^3+\left(a-b\right)^3-2a^3\)

\(=a^3+3a^2b+3ab^2+b^3+a^3-3a^2b+3ab^2-b^3-2a^3\)

\(=6ab^2\)

b: \(B=\left(2x-1\right)\left(4x^2+2x+1\right)-8\left(x+2\right)\left(x^2-2x+4\right)\)

\(=8x^3-1-8\left(x^3+8\right)\)

\(=8x^3-1-8x^3-64=-65\)

c: \(C=\left(x+2y\right)\left(x^2-2xy+4y^2\right)+\left(2x-y\right)\left(4x^2+2xy+y^2\right)-9x^3\)

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

\(=x^3+8y^3+8x^3-y^3-9x^3=7y^3\)

( x + 2y )² - ( 2x - y ) ( x + 2y ) 

= ( x + 2y ) ( x + 2y - 2x + y )

= ( x + 2y ) ( 3y - x )

Tại x = 3 

=> ( 3 + 2y ) ( 3y - 3 )

Theo mik là vậy nha :D

Hình như bạn thiếu y nha bn

Trả lời:

\(x^2\left(x+y\right)+y^2\left(x+y\right)+2x^2y+2xy^2\)

\(=x^3+x^2y+xy^2+y^3+2x^2y+2xy^2\)

\(=x^3+y^3+3x^2y+3xy^2\)