已知A=x的二次方-y的二次方,B=4xy-y的二次方.求 2A-{B-[A-(2A+B]}
问题描述:
已知A=x的二次方-y的二次方,B=4xy-y的二次方.求 2A-{B-[A-(2A+B]}
答
2A-{B-[A-(2A+B]}
=2A-{B-[A-2A-B]}
=2A-{B+A+B}
=2A-A-2B
=A-2B
∵A=x²-y²,B=4xy-y²
∴原式=x²-y²-2(4xy-y²)
=x²-y²-8xy+2y²
=x²-8xy+y²