初中文言文完全解读:一道数学题 急用

4X^2-Y^2-(4Y^2-X^2)=5X^2-3Y^2=5-12=-7
4-X^2+(Y^2-4)=8-X^2+Y^2=8-1+1/4

（2x-y）(y+2x)-(2y+x)(2y-x)
=2xy+4x2-y2-2xy-4y2+x2
=5x2-5y2 将x=1,y=2.代入得
=5-20
=-15
(2-x)(x+2)+(-y-2)(2-y)
=2x+4-x2-2x-4+y2
=y2-x2 将x=-1,y=1/2代入得
=1/4-1
=-3/4

（2x-y）(y+2x)-(2y+x)(2y-x)
=(2x-y)(2x+y)-(2y+x)(2y-x)
=4*x^2-y^2-4*y^2+x^2
=5*x^2-5*y^2
=5*(x+y)(x-y) 其中x=1,y=2
=5*(1+2)(1-2)
=5*3*(-1)
=-15
(2-x)(x+2)+(-y-2)(2-y)
=(2-x)(2+x)-(2+y)(2-y)
=4-x^2-4+y^2
=y^2-x^2
=(y-x)(y+x) 其中x=-1,y=1/2
=(1/2+1)(1/2-1)
=(3/2)(-1/2)
=-3/4

（2x-y)(y+2x)-(2y+x)(2y-x)
=2X的平方-Y的平方-(2Y的平方-X的平方)
=4X的平方-Y的平方-(4Y的平方-X的平方)
=4X的平方-Y的平方-4Y的平方+X的平方
=5X的平方-5Y的平方
=5×(1-2的平方)
=-15
(2-x)(x+2)+(-y-2)(2-y)
=(2-x)(x+2)-(2+Y)(2-Y)
=4-X的平方-(4-Y的平方)
=4-X的平方-4+Y的平方
=Y的平方-X的平方
=(1/2)的平方-1
=1/4-1
=-3/4

(2x-y)(2x+y)-(2y+x)(2y-x) (2-x)(x+2)+(-y-2)(2-y)
=((2x)^2-y^2)-(2y^2-x^2) =(2-x)(2+x)-(2+y)(2-y)
=(4x^2-y^2)-(4y^2-x^2) =(2^2-x^2)-(2^2-y^2)
=4x^2-y^2-4y^2+x^2 =4-x^2-4+y^2
=5x^2-5y^2 =4-4-x^2+y^2
=5*1^2-5*2^2 =-x^2+y^2
=5-20 =-(1)^2+(1/2)^2
=-15 =-1+1/4
=-3/4

（2x-y）(y+2x)-(2y+x)(2y-x)
=2xy+4x2-y2-2xy-4y2+x2
=5x2-5y2 将x=1,y=2.代入得
=5-20
=-15
(2-x)(x+2)+(-y-2)(2-y)
=2x+4-x2-2x-4+y2
=y2-x2 将x=-1,y=1/2代入得
=1/4-1
=-3/4