二重积分 3x 2y,坐标轴与x y=2
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(1)4ab+8-2b2-9ab-6=-2b2-5ab+2(2)原式=3x2y-2x2y+6xy-3x2y+xy=-2x2y+7xy,当x=-1,y=-2时,原式=-2×(-1)2(-2)+7×(-1
[x(x2y2-xy)-y(x2+x3y)]÷3x2y,=(x3y2-x2y-x2y-x3y2)÷3x2y,=-2x2y÷3x2y,=-23.
因为A+B+C=x3-2y3+3x2y+xy2-3xy+4+y3-x3-4x2y-3xy-3xy2+3+y3+x2y+2xy2+6xy-6=1,所以,对于x、y、z的任何值A+B+C是常数.
①x2y+xy2=xy(x+y)=1×3=3;②x2+y2=(x+y)2-2xy=32-2×1=7.
原式=2x2y+2xy-3x2y-3xy-4x2y=-5x2y-xy当x=-2,y=12时,原式=-9.
多项式x2y-2xy+3的是三次三项式,二次项的系数是-2.
原式=4x2y-6xy+3(4xy-2)+x2y+1=5x2y+6xy-5当x=2,y=-12时,原式=5×4×(-12)+6×2×(-12)-5=-21.
那个2是平方吧?可以用^代替原式=x^y+xy^=xy(x+y)=-3*6=-18
3xy(x²y-xy²+xy)-xy²(2x²-3xy+2x)=3x³y²-3x²y³+3x²y²-
∵2x+y=4,xy=3,∴2x2y+xy2=xy(2x+y)=3×4=12.故答案为:12
x=2013,y=2013[3x(x²y-xy²)+xy×(3xy-2x²)]/(x²y)=[3x²y(x-y)+x²y×(3y-2x)]/
答案:2x^2y+2xy^2原式=4x2y-{x2y-[3xy2-2x2y+4xy2+x2y]}-5xy2=4x2y-{x2y-[7xy2-x2y]}-5xy2=4x2y-{x2y-7xy+x2y]}
原式=(x3y2-x2y-x2y+x3y2)÷3x2y=(2x3y2-2x2y)÷3x2y=23xy-23.
楼上错了z=9-x^2-4y^2与xy平面围成的立体即z=9-x^2-4y^2>=0x^2+4y^2
原式=3x2y-[2xy-2xy+3x2y+xy],=3x2y-3x2y-xy,=-xy,当x=3,y=-13时,原式=-3×(-13)=1.
原式=2x2y+2xy-3x2y+3xy-4x2y=-5x2y+5xy,当x=-1,y=1时,原式=-5×(-1)2×1+5×(-1)×1=-5-5=-10.
原式=-xy(x-y),当x-y=3,xy=-2时,则原式=-3×(-2)=6.故答案为:6.
由题意得:3C=A+B=8x2y-6xy2-3xy+7xy2-2xy+5x2y=13x2y+xy2-5xy,∴C=13x2y+xy2−5xy3,故:C-A=13x2y+xy2−5xy3-(8x2y-6
解3xy²-[2xy²-2(xy-1.5x²y)]+xy-3x²y=3xy²-(2xy²-2xy+3x²y)+xy-3x²
2x2y与3x2y是同类项.2x2y+3x2y=5x2y.