x-5y=15-搜答案-大师作文网

|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=

x-y+5x-4x= ?

x-y+5x-4x=2x-y

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

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

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=5; x^y+y^x=17

X=2,Y=3或X=3,Y=2

x-y / 5y= (y-x)^2 / ( )

x-y/5y=(x-y)(x-y)/(5y(x-y))=(y-x)^2/(5y(x-y))

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

化简x+y=105x+7y=625x+5y+2y=622y=62-50y=6x=4

X^2表示平方X^2+4X+4+Y^2-2Y+1=0(X+2)^2+(Y-1)^2=0因为平方大于=0所以X+2=0Y-1=0X=-2Y=1X^2+Y^2=5

解由（1）得-15x=4y^2-4x^2由（2）得-5x=4xy+4y^2所以4y^2-4x^2=3（4xy+4y^2）所以2y^2+3xy+x^2=0所以2y+x=0或x+y=0（舍去）所以x=-2

4x=5y,x/y=5/4(x+y)/y=x/y+1=5/4+1=9/4

x²+y²=19(x+y)²=x²+y²+2xy=25xy=3(x-y)*(x-y)=(x-y)²=x²+y²-2xy=

解(x-y)(x+y)-(x-2y)²+x(3x-5y)-(x-y)(x-2y)=(x²-y²)-(x²-4xy+4y²)+(3x²-5xy

只需要把方程加减消元就可以咯

（5x+3y)(3y-5x)-(4x-y)(4y+x)=(3y)^2-(5x)^2-(4x^2+15xy-4y^2)=9y^2-25x^2-4x^2-15xy+4y^2=13y^2-15xy-29x^

Y={X (-5

用switch写：functiony=f(x)flag=(x>-5)*(x0)*(x-5)&&(x0)&&(x

因为x的平方-y的平方=15所以x的平方是正数,y的平方是正数因为x的平方-y的平方=（x+y）乘（x-y）所以x-y=3选我!

展开x^2-2y^2-xy=-5x^2-2y^2+xy=7所以x^2-2y^2=1xy=6上式除以下式,解分式方程x/y=3/2或-4/3(舍去)所以x^2=9y^2=4x=3y=2或x=-3y=-2