30X 21Y=213,X=?Y=?-搜答案-大师作文网

x+x+x+y+y=54,x+x+y+y+y=56得出3X+2Y=54,2X+3Y=56扩大后得出6X+4Y=108,6X+9Y=118两式相减得出Y=2得出X=50/3

(x+y-z)(x-y+z)=

[x+(z-y)][x-(z-y)]=x-(z-y)记得采纳啊

x+y=20-6 3x+y=30

x+y=20-6=14x+y=14x=14-y3(14-y)+y=3042-3y+y=3042-2y=302y=12y=6x=8

(x-y)(x+y)(xx-yy)=?

(x-y)(x+y)(xx-yy)=(x^2-y^2)(x^2-y^2)=x^4-2x^2y^2+y^4

x(x-y)+y(y-x)=x(x-y)-y(x-y)=(x-y)(x-y)=(x-y)²明教为您解答,请点击[满意答案];如若您有不满意之处,请指出,我一定改正!希望还您一个正确答复!祝您

y'-2y=(e^x)-x

首先求齐次方程通y'-2y=0特征方程：x-2=0x=2为特征根∴y=Ce^(2x)设方程的一个特解为y=Ae^x+ax+b代入方程：Ae^x+a-2Ae^x-2ax-2b=-Ae^x-2ax+a-2

令a=x²+y²则a²-a=12a²-a-12=0(a-4)(a+3)=0a=4,a=-3平方数大于等于0所以a=-3不成立所以x²+y²=

x+y=450;40%x+30=60%y

x＋y＝450①0.4x﹣0.6y＝﹣30②①×0.40.4x＋0.4y＝180③③﹣②y＝210代入①x＝240即方程组的解为x＝240,y＝210,用几何方法表示是第一象限的点（240,210）

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

X=2,Y=3或X=3,Y=2

求y'=y/(y-x)

∵令y=xt,则y'=xt'+t代入原方程,得xt'+t=t/(t-1)==>xt'=(2t-t^2)/(t-1)==>(t-1)dt/(2t-t^2)=dx/x==>2dx/x+[1/t+1/(t-

X+Y分之X-Y等于3x=-2yX+Y分之2(x-y)减X+Y分之3X+Y=(-x-3y)/(x+y)=1

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

先一个一个的展开括号项,再同项合并就行了啊[x(x-y)-y(x-y)+(x+y)(x-y)]÷2x=[xx-xy-(xy-yy)+x(x-y)+y(x-y)]÷2x=[xx-xy-xy+yy+xx-

应该是4x+2y=304x+y=22吧再问：��x��y�ֱ��Ƕ��١�再答：4x+2y=224x+y=30�ó�y=22-30=-8��y=-8��뵽4x+2y=22�еó�4x+��-16��

5(x+y)+3(x-y)=908x+2y=901式5(x+y)-3(x-y)=302x+8y=302式1式乘以4-2式解得x=11y=1

y'+2y/x=x通解

（0.2x+0.1y）/2-（4x-y）/10=（x-y）/5+(3x+0.5y)/30①(3x+2y-1)/8=3-(0.8x-5y)/41②①两边同时乘以60得（6x+3y）-（24x-6y）=（

|x|+|y|=30①2|x|-3|y|=20②①*2-②得5|y|=40|y|=8①*3+②得5|x|=110|x|=22x=±22y=±8

假设：X=Y/XY=X/Y带入函数就是：F(y/x,x/y)=（y/x+x/y）/(y/x—x/y)=x²+y²)/(y²-x²)希望可以帮助你!

) y=cos(x-y)

1.两边求导得：y'=-sin(x-y)(1-y')解得y'=sin(x-y)/[sin(x-y)-1]2.y'=-e^-xy''=e^-xy'"=-e^-x3.y'"=(e^2x)'"(sinx)+