题目内容
已知M=x2-xy,N=xy+y2,则M+N=________,M-N=________,3M-2N=________.
答案:
解析:
提示:
解析:
x2+y2,x2-2xy-y2,3x2-5xy-2y2 |
提示:
提示:M+N=(x2-xy)+(xy+y2)=x2+xy-xy+y2=x2+y2; M-N=(x2-xy)-(xy+y2)=x2-2xy-y2; 3M-2N=3(x2-xy)-2(xy+y2)=3x2-3xy-2xy-2y2=3x2-5xy-2y2. |
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