题目内容
5x2-3xy+y2与一个多项式的和是3xy-x2,则这个多项式是
A.6x2-6xy+y2
B.-6x2+6xy-y2
C.4x2+y2
D.-6x2+y2
已知x2+y2=7,xy=-2.
求5x2-3xy-4y2-11xy-7x2+2y2的值.