由方程x 2y=6 2 y=9
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将z对x的偏导记为dz/dx,(不规范,请勿参照)(e^x)-xyz=0两边对x求导数(e^x)'-(xyz)'=0e^x-x'yz-xy(dz/dx)=0e^x-yz-xy(dz/dx)=0xy(d
x+y+xy=9x+y=9-xyx^2y+xy^2=20xy(x+y)=20xy(9-xy)=20xy^2-9xy+20=0(xy-4)(xy-5)=0xy=4或xy=5x+y=5或x+y=4x^2+
原式=2x2y+2xy-3x2y-3xy-4x2y=-5x2y-xy当x=-2,y=12时,原式=-9.
把X=3;Y=-2代入即可解
∵xy+x+y+7=0  
(X^2-y+1)(X^2+1)+X^2y+y-X^2=(X^2-y+1)(X^2+1)+(X^2+1)y-X^2=(X^2-y+y+1)(X^2+1)-X^2=(X^2+1)^2-x^2=(x^2+
(2x3-3x2y-2xy2)-(x3-2xy2+y3)+(-x3+3x2y-y3)=2x3-3x2y-2xy2-x3+2xy2-y3-x3+3x2y-y3=-2y3=-2×(-1)3=2.因为化简的
(x2y)(xy2)=xy*xy*xy=6*6*6=216楼主是不是抄错题了?(x2y)+(xy2)=xy(x+y)=5*6=30
(X+Y)2=1402X2Y*3=14400(X+Y)2=140→X+Y=70→Y=70-X①2X2Y*3=14400→XY=1200②把①代人②得:X(70-X)=1200X²-70X+1
对y^2-2xy=7求微分,得2ydy-2(ydx+xdy)=0,∴(y-x)dy=ydx,∴dy/dx=y/(y-x).
隐函数直接求导数.e^(x+y)(1+y')-sin(xy)(y+xy')=0解出y'即为dy/dx=[e^(x+y)-y*sin(xy)]/[e^(x+y)-x*sin(xy)]
再问:y²+2㏑y求导不是2y+2/y吗?y'是怎么来的?
x2y+xy2=xy*(x+y)因为x+y=-(7+xy)又x+y=(9+2xy)\3所以(9+2xy)\3=-(7+xy)3+2xy\3=-7-xy5xy\3=-10解得xy=-6所以x+y=-(7
IIA族均为金属,形成化合物时显+2价,而Y为VIIA族元素,又X为正价,所以Y为负价,且为-1价,故选A:XY2.
因为x^2y+xy^2=30,xy(x+y)=30,xy=6x+y=5所以(x+y)^2=x^2+y^2+2xy=x^2+y^2+12=25所以x^2+y^2=13所以(x-y)^2=x^2+y^2-
两边对【x】求导,注意,y是x的函数,利用复合函数求导1/[1+(y/x)^2]×(y/x)'=1/2×1/(x^2+y^2)×(x^2+y^2)',也就是:x^2/(x^2+y^2)×(xy'-y)
原式=2x2y-2xy2+3x2y2-3x2y-3x2y2+3xy2=-x2y+xy2,当x=-12,y=2时,原式=-(−12)2×2+(-12)×22=-52.
(x+2)²+|y-1|=0平方数与绝对值都是非负数两个非负数的和为0,那么这两个数都是0x+2=0y-1=0解得:x=-2,y=1x³+3x²y+3xy²+y
X2Y为Na2S,XY2为CS2.离子化合物为硫化钠na2s,共价为二硫化碳cs2再问:如何用电子式表示cs2的形成过程