计算[(x+2y)^2-(x+y)(3x-y)-5y]/2x,其中x=-2,y=1/2
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计算[(x+2y)^2-(x+y)(3x-y)-5y]/2x,其中x=-2,y=1/2
![计算[(x+2y)^2-(x+y)(3x-y)-5y]/2x,其中x=-2,y=1/2](/uploads/image/z/17518904-8-4.jpg?t=%E8%AE%A1%E7%AE%97%5B%28x%2B2y%29%5E2-%28x%2By%29%283x-y%29-5y%5D%2F2x%2C%E5%85%B6%E4%B8%ADx%3D-2%2Cy%3D1%2F2)
[(x+2y)²-(x+y)(3x-y)-5y]/2x
=[(x²+4xy+4y²)-(3x²-xy+3xy+y²)-5y]/2x
=(-2x²+2xy+3y²-5y)/2x
=-x+y+3y²/2x-5y/2x
将x=-2,y=1/2代入上式得:
[(x+2y)²-(x+y)(3x-y)-5y]/2x
=2+1/2+(3/4)/(-4)+(5/2)/4
=47/16
=[(x²+4xy+4y²)-(3x²-xy+3xy+y²)-5y]/2x
=(-2x²+2xy+3y²-5y)/2x
=-x+y+3y²/2x-5y/2x
将x=-2,y=1/2代入上式得:
[(x+2y)²-(x+y)(3x-y)-5y]/2x
=2+1/2+(3/4)/(-4)+(5/2)/4
=47/16
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