将 x=1 y=3 和 x=3 y=5 代入方程ax by=30
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![将 x=1 y=3 和 x=3 y=5 代入方程ax by=30](/uploads/image/f/3949343-71-3.jpg?t=%E5%B0%86+x%3D1+y%3D3+%E5%92%8C+x%3D3+y%3D5+%E4%BB%A3%E5%85%A5%E6%96%B9%E7%A8%8Bax+by%3D30)
|x|=3x=3或-3|y|=5y=5或-5|x-y|=|x|+|y||x|=3|y|=5|x|+|y|=8|x-y|=8x-y=8或-8由此可得y=5x=-3或y=-5x=3x+y=2或-2x-y=
原式=(9x²+24xy+16y²-4x²+y²-5x²+6xy-y²)÷(-2y)=(30xy+16y²)÷(-2y)=-15x
3(x+y)+3(y-x)=1(1)3(x+y)+4(y-x)=-1(2)(2)-(1)得y-x=-2(3)代入(1)3(x+y)-6=1x+y=7/3=>x=7/3-y又由(3)得x=y+2y+2=
5x-12y=23,x=(23+12y)/53(23+12y)/5+8y=1069+36y+40y=5076y=-19y=-1/4.x=(23-3)/5=4.x=4,y=-1/4.
设x-y=mx+y=n则6m-2n=143m+n=5解得m=2n=-1即x-y=2x+y=-1解得x=1/2y=-3/2
很多数学符号,还是写出来方便.
因为(x-y)/(x+y)=3,则(x+y)/(x-y)=1/3则5(x-y)(x+y)-(x+y)/2(x-y)=5*3-1/(3*2)=15-1/6=89/6
(2x+(y-1))(2x-(y-1))=4x^2-(y-1)^2(3x+y)(3x-y)=9x^2-y^2相减得4x^2-y^2+2y-1-9x^2+y^2=-5x^2+2y-1带入得-5*1/25
x+y=0x=-yx/y=y/x=-13x-10+3y+y/5x=3(x+y)-10+y/5x=0-10-1/5=-10.2
x:y=2:3和5x+3y=38y=3x/2;5x+3y=385x+9x/2=3819x=76x=4y=63y+x/y=8和9y-2x/y=96y+2x/y=16;9y-2x/y=915y=25y=5
解(x-y)(x+y)-(x-2y)²+x(3x-5y)-(x-y)(x-2y)=(x²-y²)-(x²-4xy+4y²)+(3x²-5xy
3X+4Y=23X=2-4YX=(2-4Y)/3X-Y-1/7D
画出限定区域如图z=(x+y)/x =1+y/xy/x=(y-0)/(x-0)看成区域点与原点连线的斜率显然在A(1,2)斜率有最大值=2在(2,1)斜率有最小值=1/2∴z最大值=2+1=
将3x-y=7和2x+y=8组成方程组得,3x-y=72x+y=8,解得,x=3y=2,将x=3y=2分别代入ax+y=b和x+by=a得,3a+2=b3+2b=a,解得a=-75b=-115.
完整设1/(x+y)=a,1/(x-y)=b原方程组可变为4a+6b=39b-a=1a=9b-136b-4+6b=3b=1/6,a=1/2x+y=2x-y=6所以原方程组的解为:x=4,y=-2
5x=y,5:y=x,3x=4y,3:x=4:y,3;x=y:43x+4x=y,中X和Y成比例分别成正比反比正比正比反比正比3x+4x=y确定没抄错?要是抄错了就不成比例了因为Y比X得一个常数才能叫成
(x+y)/2+(x-y)/6=1x/2+x/6+y/2-y/6=12x/3+y/3=12x+y=3(1)3(x+y)-4(x-y)=43x+3y-4x+4y=4-x+7y=4(2)(1)+2*(2)
原式=x-x+x-x+……-x+(2-1+4-3+5-4+……+2008-2007-2009)y=0+(1×1004-2009)y=-1005y=1005/2