化简求值(1)2x^2y(-2xy^2)^3+(2xy)^3(-xy^2)^2,其中x=3,y=1/4
(2)(1/3xy)^2(xy(2x-y)-2x(xy-y^2)),其中x=-1又二分之一,y=-2...
(2)(1/3xy)^2(xy(2x-y)-2x(xy-y^2)),其中x=-1又二分之一,y=-2
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解:⑴2x^2y(-2xy^2)^3+(2xy)^3(-xy^2)^2
=2x^2y·﹙﹣8x^3y^6﹚+8x^3y^3·x^2y^4
=﹣16x^5y^7+8x^5y^7
=﹣8x^5y^7
当x=3,y=1/4时原式=﹣8x^5y^7=﹣8×3^5×﹙1/4)^7=﹣243/2048
⑵(1/3xy)^2(xy(2x-y)-2x(xy-y^2))
=1/9x²y²[2x²y-xy²-2x²y+2xy²]
=1/9x²y²·xy²
=1/9x^3y^4
当x=﹣3/2,y=﹣2时
原式=1/9x^3y^4
=1/9×﹙﹣3/2﹚^3×﹙﹣2﹚^4
=1/9×﹙﹣27/8﹚×16
=﹣6
=2x^2y·﹙﹣8x^3y^6﹚+8x^3y^3·x^2y^4
=﹣16x^5y^7+8x^5y^7
=﹣8x^5y^7
当x=3,y=1/4时原式=﹣8x^5y^7=﹣8×3^5×﹙1/4)^7=﹣243/2048
⑵(1/3xy)^2(xy(2x-y)-2x(xy-y^2))
=1/9x²y²[2x²y-xy²-2x²y+2xy²]
=1/9x²y²·xy²
=1/9x^3y^4
当x=﹣3/2,y=﹣2时
原式=1/9x^3y^4
=1/9×﹙﹣3/2﹚^3×﹙﹣2﹚^4
=1/9×﹙﹣27/8﹚×16
=﹣6
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(1)
2x^2y(-2xy^2)^3+(2xy)^3(-xy^2)^2
=-2x^2y(2xy^2)^3+(2xy)^3(xy^2)^2
=-16x^5y^7+8x^5y7
=-8x^5y^7
=-8*3^5*(1/4)^7
=-2*(3/4)^5
(2)
(1/3xy)^2(xy(2x-y)-2x(xy-y^2))
=(1/3xy)^2(xy(2x-y)-2xy(x-y))
=(1/3xy)^2(xy(2x-y-2x+2y))
=(1/3xy)^2(xy^2)
=(x^3y^4)/3
=(-27/8*16)/3
=-18
2x^2y(-2xy^2)^3+(2xy)^3(-xy^2)^2
=-2x^2y(2xy^2)^3+(2xy)^3(xy^2)^2
=-16x^5y^7+8x^5y7
=-8x^5y^7
=-8*3^5*(1/4)^7
=-2*(3/4)^5
(2)
(1/3xy)^2(xy(2x-y)-2x(xy-y^2))
=(1/3xy)^2(xy(2x-y)-2xy(x-y))
=(1/3xy)^2(xy(2x-y-2x+2y))
=(1/3xy)^2(xy^2)
=(x^3y^4)/3
=(-27/8*16)/3
=-18
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