Question

a. (x+y)\(^2\) - (x-y)\(^2\)

b. 2(x-y)(x+y)+(x+y)\(^2\) + (x-y)\(^2\)

Answer 1

Câu a :

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

Câu b :

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

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

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

\(=4x^2\)

Answer 2

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

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

\(=4xy\)

Answer 3

Hai phép này đều áp dụng hằng đẳng thức nhé!

a, (x+y)² -(x-y)²

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

= 2x.2y

=4xy

b, 2(x-y)(x+y) +(x+y)² + (x-y)²

= (x-y)² + 2(x-y)(x+y) + (x+y)²

= (x-y+x+y)²

=(2x)²

=4x²