Question

mn ơi giúp mình câu này với:((   

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

 

Answer 1

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

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

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

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

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

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