(5x-2y)²-(2x-y)(2x-3y)+(2x+y)(x-y)
=(25x²-20xy+4y²)-(4x²-8xy+3y²)+(2x²-xy-y²)
=25x²-20xy+4y²-4x²+8xy-3y²+2x²-xy-y²
=23x²-13xy这是什么啊？好多奇怪的符号(5x-2y)平方-(2x-y)(2x-3y)+(2x+y)(x-y)
=(25x平方-20xy+4y平方)-(4x平方-8xy+3y平方)+(2x平方-xy-y平方)
=25x平方-20xy+4y平方-4x平方+8xy-3y平方+2x平方-xy-y平方
=23x平方-13xy