x=1 1/y，y=1 1/x，则y等于

3x-2y=153y-2x=11两式相加可得x+y=26

y=3x/5原式=x/(x+3x/5)+(3x/5)/[x-3x/5]-(9x^3/25)/(x^3-9x^3/25)=8/3-3/2-9/16=29/48

(x+y)/x=11/88x+8y=11y8x=3yy=8x/3(x-y)/(x+2y)=(x-8x/3)/(x+16x/3)=(-5x/3)/(19x/3)=-5/19

化简得：-x+7y=11①7x+3y=27②①式×7得：-7x+49y=77③②+③得：52y=104∴y=2代入①得：x=3∴x=3,y=2再问：亲，是代入法哦！再答：代入法①式得3x+3y-4x+

x*y+(x+y)*(x-y)=(x+y)-(x-y)+（x+y+x-y)-(x+y-x+y)=-2y+2x-2y=2x-4y

tanx=sinxcosx=x∴sinx=xcosx同理，siny=ycosy所以原式=sinxcosy+cosxsinyx+y-sinxcosy−cosxsinyx−y=xcosxcosy−ycos

联立两个方程7x+3y=44(1)11x+2y=61(2)将方程（1）左右两边同时乘以2,方程（2）左右两边同时乘以3原方程组化为14x+6y=88(3)33x+6y=183(4)用方程（4）-（3）

1.1/x+1/y=(x+y)/xy=-1/(x+y)去分母可得,（x+y)^2+xy=0即x^2+y^2=-3xy所以y/x+x/y=(x^2+y^2)/xy=-32.由1/x-1/y=5可得y-x

（11x+y)(-11x+y)+(11x+y)的平方=y^2-(11x)^2+(11x)^2+y^2+2*11xy=2y^2+22xy（x-2y)(x+2y)-(x+2y)的平方-（x-2y)(2y-

(1){x=y-3{x+y=11y-3+y=112y=14y=7x=y-3=7-3=4所以原方程组的解为x=4,y=7(2){2x+y=13{3x-2y=8y=13-2x3x-2(13-2x)=83x

X=6,Y=5或X=6,Y=-5X(X+Y)-Y(X+Y)=X*X+XY-XY-Y*Y=X*X-Y*Y=(X-Y)(X+Y)=11所以（X-Y）=1,（X+Y）=11或（X-Y）=11,（X+Y）=1

方程化为－x+7y=1117x+3y=272将1式化为x=7y-113则将3式代入2式可得7（7y-11）+3y=2752y=104y=2x=7×2-11x=3所以解得x＝3y＝2

=[(8x-8y)+(2x-3y)]/(x-y)=[(8x-8y)+0]/(x-y)=(8x-8y)/x-y=8(x-y)/x-y(这是乘法分配律)=8(约分同时除以x-y)

①x+y=5②3x-7y=11将①×7得：③7x+7y=35用②+③得：④3x-7y+7x+7y=11+35,即10x=46,即x=4.6代入①得：y=5-x=0.4

若(x-y)/(x+y)=3那么x-y=3(x+y)x-y=3x+3y故x=-2y所以(x+2y)/(6x-7y)=(-2y+2y)/(6*(-2y)-7y)=0如果不懂,请Hi我,祝学习愉快!

3x+4y=96x+5y=27两式相加得：9x+9y=36则：9(x+y)=36所以,x+y=4所以,11x+11y=11(x+y)=44

x+y/y=11/8说明11y=8（x+y）即8x=3y所以x-y/x+2y=3（x-y）/3(x+2y)=（3x-3y）/(3x+6y)=(3x-8x)/(3x+16x)=-5/19

已知x+3y+z=11x+y=7,则7x+10y+3z=40

x+y/3=x-y/4⑴2x+3y=11⑵由⑴得x+7y=0,x=-7y(3)将(3)代入⑵得y=-1所以x=7

化简得：-x+7y=11①7x+3y=27②①式×7得：-7x+49y=77③②+③得：52y=104∴y=2代入①得：x=3∴x=3,y=2