B={X∑Z -33-搜答案-神马作文网

令a/(x-y)=b/(y-z)=c/(z-x)=ma=m(x-y)b=m(y-z)c=m(z-x)a+b+c=m(x-y)+m(y-z)+m(z-x)=m(x-y+y-z+z-x)=m*0=0

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

[x+(z-y)][x-(z-y)]=x-(z-y)记得采纳啊

B={x∈Z|-3

再化简B有B={x∈Z|-1

B设a=2k,b=2t+1a+b=2k+2t+1=2(k+t)+1k+tεZ

1.x=1,y=2,z=-12.x=-1,y=-3,z=23.a=-5/2,b=7/2,c=2其他的我也不说了,慢慢想吧~

B是什么,没写清楚.b里面是根号（1-x^2）?x是A里面的?再问：B={Y|Y=根号}就是根号下是1-x^2，是1-x^2的全部在根号下，题目就是这样再答：A=(1,2)，如果y里的x是A里的，那Y

cov(x,z)=cov(x,5x+2)=cov(x,5x)+cov(x.2)=5cov(x,x)+0=5Dx=5np(1-p)=5*3*0.2*0.8=0.24

udong

A=全集-{X=z}求概率,加个P就好了呀!

A={X|X^2-3X+2

X-Y+Z=A1X+Y-Z=B2-X+Y+Z=C31+2+3:x+y+z=A+B+C4(4-1)/2:y=(B+C)/2(4-2)/2:z=(A+C)/2(4-3)/2:x=(A+B)/2

U还是整数集啊A和B在这里是干扰的,根本对U没有影响,反而是受限于U的

是的solve(f3)ans=3.9445465689598833643734182162712-0.74568267970128715013587848090705-1.27941151933974

令a-b/x=b-c/y=c-a/z=K所以x=a-b/k,y=b-c/k,z=c-a/kx+y+z=(a-b+b-c+c-a)/k=0

设x/(a-b)=y/(b-c)=z/(c-a)=k∴x=(a-b)k,y=(b-c)k,z=(c-a)k∴x+y+z=k（a-b+b-c+c-a）=0

(X+Y+Z)^2=x^2+y^2+z^2+2(xy+yz+xz)=a^2=x^2+y^2+z^2+2b所以x^2+y^2+z^2=a^2-2

楼上解法貌似不对啊.∵A={x|-2≦x≦a},B={z|z=2x+3,x∈A}∴-1≤2x+3≤2a+3即B=[-1,2a+3],同理,得当-2≤a≤2时C=[a²,4]①当a>2时,C=

1、原式=4a²+4ab+b²-(4a²-b²)=4ab+2b²2、原式=[z+(x+y)][z-(x+y)]+(x-y)²=z²

设k=(a-b)/x=(b-c)/y=(c-a)/z,则x=(a-b)/k,y=(b-c)/k,z=(c-a)/kx+y+z=(a-b+b-c+c-a)/k=0

a=X/X+Y?应为a=X/Y+Z吧!a/a+1=(X/(Y+Z))/((X/(Y+Z))+1)=X/X+Y+Zb/b+1=Y/X+Y+Zc/c+1=Z/X+Y+Z