(x+y)2 - (x−y)2
= x2 +2xy+y2 +x2 -2xy +y2
=2(x2 +y2 )
~Chúc bạn học tốt!~
(x+y)^2+(x-y)^2
=x^2+2.x.y+y^2+x^2-2.x.y+y^2
=2x^2+2y^2
=2(x^2+y^2)
Choose the best answer.
We are looking for ____ place to spend ____ night.
Please turn off ___ lights when you leave ___ room.
I like _____ colorful costumes of ____ ethnic minority people in Vietnam.