已知：A=X*X-3xy+y*y,B=2x*x+xy-3y*3y.求A+B,A-B,A+2B_数学解答

已知：A=X*X-3xy+y*y,B=2x*x+xy-3y*3y.求A+B,A-B,A+2B

人气：173 ℃　时间：2020-05-02 01:25:39

解答

A+B=(x²-3xy+y²)+(2x²+xy-9y²)=x²-3xy+y²+2x²+xy-9y²=3x²-2xy-8y²A-B=(x²-3xy+y²)-(2x²+xy-9y²)=x²-3xy+y²-2x²-xy+9y²...