4xy-5x 6y=15
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1.2(Xy+Xy)-3(Xy-xy)-4Xy=2*2xy-0-4xy=4xy-4xy=02.1/2ab-5aC-(3acb)+(3aC-4aC)=1/2ab-5ac-3acb-ac=1/2ab-6a
Solution:x^2-2xy+3y^2=9(1)4x^2-5xy+6y^2=30(2)Eq(1)*5-Eq(2)*2,wehavex^2-y^2=5(3)Eq(2)-Eq(1),wegetx^2+
(x+2)^2+|y+1|=0x=-2,y=-15xy²-{2xy²-[3xy²(4xy²-2x²y)]}=5xy²-2xy²+3
8x的平方-13xy-15y的平方=4M-N再问:详细过程呢??再答:4(3x的平方-2xy-4xy的平方)-(4x的平方+5xy-y的平方)=12x的平方-8xy-16xy的平方-4x的平方-5xy
A、原式=-6x2-19xy-5y2;B、原式=2x2-9xy-7y2;C、原式=x2-16xy-10y2;D、原式=8x2-13xy-15y2.故选D.
5xy+4x+7y+6x-3xy-4xy+3y=5xy-3xy-4xy+4x+6x+7y+3y=(5-3-4)xy+(4+6)x+(7+3)y=-2xy+10x+10y=-2xy+10(x+y)因为x
可以先设xy=t原式=[4(t-1)^2-(t+2)(2-t)]/(1/4*t)=4(4t^2-8t+4-2t+t^2-4+2t)/t=4(5t^2-8t)/t=(20t-32)/t=20-32/t将
原式=[4(x+y)-2xy]分之[(x+y)+xy]=[4(3xy)-2xy]分之[(3xy)+xy]=10xy分之2xy=5分之1
化简结果是:-20xy+32代入得40
先把代数式(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)化简(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)=5XY+4X+7Y+6X-3XY-4XY+3Y=-2XY+10X+1
(7xy+4x-7y)+(6x-3xy)-(3y+4xy)=7xy+4x-7y+6x-3xy-3y-4xy=10x-10y=10(x-y)=10*3=30
a-2b=(5x²y-3xy²+4xy)-2(7xy²-2xy+x²y)=5x²y-3xy²+4xy-14xy²+4xy-2x
[4(xy-1)^2-(xy+2)(2-xy)]除以4分之1xy=[4x^2乘以y^2-8xy+4-(4-x^2y^2)]除以4分之1xy=(4x^2乘以y^2-8xy+4-4+x^2y^2)除以4分
(5xy+4x+7y)+(6x-3xy)-(4xy-3y)=5xy+4x+7y+6x-3xy-4xy+3y=(5xy-3xy-4xy)+(4x+6x)+(7y+3y)=-2xy+10x+10y=-2x
求xy的最大值就是求4xy的最大值就是求x.(4y)的最大值.记z=4y,原方程写做x+z+5=(xz)/4.所以xz=4(x+z+5).也就是说,x和z是下面这个方程的根:a^2-b.a+4(b+5
已知A=5x^2y-3xy^2+4xy,B=7xy^2-2xy+x^2y.(1)求A-2B的值A-2B=5x^2y-3xy^2+4xy-2*(7xy^2-2xy+x^2y)=5x^2y-3xy^2+4
因为x、y都是正数,则:x+4y≥4√(xy)设:√(xy)=t,则:xy=4y+x+5≥4√(xy)+5即:t²≥4t+5t²-4t-5≥0t≤-1或t≥5因为:t=√(xy)≥
5x²+5xy+y²+2x+1=04x²+y²+4xy+2x+x²+1=0(2x+y)²+(x+1)²=0得{2x+y=0---①