(x-2y)2+(x+2y)(x-2y)-(x-3y)(x-y)计算结果是什么?x等于-4,y等于0.5代入后是多少第一个括号后的2是平方意

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(x-2y)2+(x+2y)(x-2y)-(x-3y)(x-y)计算结果是什么?x等于-4,y等于0.5代入后是多少第一个括号后的2是平方意
(x-2y)2+(x+2y)(x-2y)-(x-3y)(x-y)计算结果是什么?x等于-4,y等于0.5代入后是多少第一个括号后的2是平方意

(x-2y)2+(x+2y)(x-2y)-(x-3y)(x-y)计算结果是什么?x等于-4,y等于0.5代入后是多少第一个括号后的2是平方意
(x-2y)²+(x+2y)(x-2y)-(x-3y)(x-y)
=x²-4xy+4y²+x²-4y²-x²+4xy-3y²
=x²-3y²
x=-4,y=0.5
代入原式=（-4）²-3（0.5）²=16-0.75=15.25

x^2-3y^2

(x-2y)^2+(x+2y)(x-2y)-(x-3y)(x-y)
=x^2-4xy+4y^2+x^2-4y^2-(x^2-xy-3xy+3y^2)
=x^2-4xy+4y^2+x^2-4y^2-x^2+xy+3xy-3y^2
=x^2-3y^2
当x=-4,y=0.5时，
原式=16-0.75=15.25

x^2-3y^2
15.25

x^2+4y^2-4xy+x^2-2xy+2xy-4y^2-x^2+3xy+xy-3y^2=x^2-3y^2
15.25

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