Question

Thu gọn biểu thức 

a) (x+y)²+(x-y)²

b) (x+y)²-(x-y)²

Answer 1

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

b: \(=\left(x+y+x-y\right)\left(x+y-x+y\right)=2x\cdot2y=4xy\)

Answer 2

a)
= x² + y² + x² - y²
= 2x² 

b) 
= x² + y² - x² + y2
= 2y²
 

Answer 3

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

 

\(\left(x+y\right)^2-\left(x-y\right)^2=\left[\left(x+y\right)-\left(x-y\right)\right].\left[\left(x+y\right)+\left(x-y\right)\right]\)

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