已知:A=3X^2+5Y^2-2XY^2,B=4X^2-2Y^2+XY^2,求1,A+B.求2,B-A
问题描述：
已知:A=3X^2+5Y^2-2XY^2,B=4X^2-2Y^2+XY^2,求1,A+B.求2,B-A
要原因,1,我算出来是7X^4+1,可答案是7X^2+3Y^2-XY^2
2,我算出来是1-7Y^2+2XY^4,是X^2-7Y^2+3X^2
还有XY^2+2XY^2到底等于几啊,是不是次数和次数相乘等于2XY^4
答
A+B=3x^2+5y^2-2xy^2+4x^2-2y^2+xy^2=(3+4)x^2+(5-2)y^2-(2-1)xy^2=
7x^2+3y^2-xy^2
B-A=(4-3)x^2-(2+5)y^2+(1+2)xy^2=x^2-7y^2+3xy^2
正确答案哈