Question

[Lê Thị Lý]

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

b,(x-y+z)^2+(z-y)^2+2.(x-y+z).(y-z)

kết quả câu a là 4x^2,câu b là x^2 nhưng mình không biết cach trình bầy nhờ mấy bạn trình bầy hộ nha

Answer 1

[Minh Anh]

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

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

\(=\left(2x\right)^2=4x^2\)

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

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

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

\(=x^2\)