要步骤 、 1 、 {(x+y)눀-(x-y)(x+3y0-5y눀}÷2y= ？ 当x=-2，y=2分之1

1，{(x+y)²-(x-y)(x+3y)-5y²}÷2y=
=(x^2+y^2+2xy-x^2-3xy+xy+3y^2-5y^2)/(2y)
=-y^2/(2y)
=-1/2y当x=-2，y=1/2时
原式=-1/4
2，（1/4a²b）×（-2ab²）²÷（-0.5a^4b^5）
=-1/4a^2b*4a^2b^4*2/(a^4b^5)
=-2,
3，4x-(-2x+3)(-2x-3)
=4x-(4x^2-9)
=4x-4x^2+9

当x=-2，y=1/2
{(x+y)²-(x-y)(x+3y)-5y²}÷2y=
=(x^2+y^2+2xy-x^2-3xy+xy+3y^2-5y^2)/(2y)
=-y^2/(2y)
=-1/2y=-1/4
（1/4a²b）×（-2ab²）²÷（-0.5a^4b^5）
=-1/4a^2b*4a^2b^4*2/(a^4b^5)
=-2
4x-(-2x+3)(-2x-3)
=4x-(4x^2-9)
=4x-4x^2+9

解:由题意得到方程组:
X/2-(Y+1)/3=1.......(1)
3X+2Y=10 .......(2)
解之:(1)---->3X-2Y=8
(2)---->3X+2Y=10
现把(1)+(2)得到:
X=3
Y=1/2