已知A=4x2-4xy+y2,B=x2+xy-5y2,求: (1)A+B (2)B-3A.
问题描述:
已知A=4x2-4xy+y2,B=x2+xy-5y2,求:
(1)A+B
(2)B-3A.
答
(1)A+B=4x2-4xy+y2+x2+xy-5y2
=5x2-3xy-4y2;
(2)B-3A=(x2+xy-5y2)-3(4x2-4xy+y2)
=x2+xy-5y2-12x2+12xy-3y2
=-11x2+13xy-8y2.