问题
选择题
把x2-2xy+y2-2x+2y的二次项放在添“+”号的括号里,把一次项放在添“-”号的括号里,按上述要求完成并正确的是[ ]
A. x2-2xy+y2-2x+2y=(x2+y2)-(2xy+2x-2y)
B. x2-2xy+y2-2x+2y=(x2-2xy+y2)-(2x-2y)
C. x2-2xy+y2-2x+2y=(x2+y2)-(-2xy-2x+2y)
D. x2-2xy+y2-2x+2y=(x2-2xy+y2)-(-2x+2y)
答案
答案:B