Question

a) A=(a+b)³ + (a-b)³

b) B=(x-y)³ + 3xy . (x+y)

Answer 1

a. A = (a + b)³ + (a - b)³

A = (a + b + a - b)\(\left[\left(a+b\right)^2-\left(a+b\right)\left(a-b\right)+\left(a-b\right)^2\right]\)

A = 2a\(\left[\left(a^2+2ab+b^2\right)-\left(a^2-b^2\right)+\left(a^2-2ab+b^2\right)\right]\)

A = 2a(a² + 2ab + b² - a² + b² + a² - 2ab + b²)

A = 2a(a² + 3b²)

A = 2a³ + 3ab²

Answer 2

ko có gì

Answer 3

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

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

\(=2a^3+6ab^2\)

b: \(B=\left(x-y\right)^3+3xy\left(x+y\right)\)

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

\(=x^3+6xy^2-y^3\)