ff(z^2-y)
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∑是循环和例如∑a=a+b+c∑a^2=a^2+b^2+c^2∑(z-y)(x-y)/(x+y-2z)(y+z-2x)=∑(z-y)(x-y)(x+z-2y)/(x+y-2z)(y+z-2x)(x+z
x²+y²+z²=2x+2y+2z(x-1)²+(y-1)²+(z-1)²=3令x=1+u,y=1+v,z=1+w==>Σ':u²
有这样的公式:a^3+b^3+c^2-3abc=(a+b+c)(a^2+b^2+c^2-ab-bc-ca)左边减右边,证明:(x+y-2z)^3+(y+z-2x)^3+(z+x-2y)^3-3(x+y
x2-(y+z)2=(x+y+z)(x-y-z)=8x+y+z=2所以x-y-z=8÷2=4
∵x-2y+z=(x-y)-(y-z),x+y-2z=(y-z)-(z-x),y+z-2x=(z-x)-(x-y).设x-y=a,y-z=b,z-x=c,则原式=-ac/(a-b)(b-c)+(-ba
正整数?取对数即证:2xlnx+2ylny+2zlnz>(y+z)lnx+(x+z)lny+(x+y)lnzx>y>z,lnx>lny>lnz由排序不等式得xlnx+ylny+zlnz>ylnx+zl
=(x+y+z)^2+yz(y+z+x)=(x+y+z)(x+y+z+yz)
解①原式={(2y-z)×[2y(z+2y)+z²]}²={(2y-z)[(2y)²+2yz+z²]}²=[(2y)³-z³]
4X^2-8X+1+8X^2+8X=12X^2-48X+48+348X=54X=9/8
第一个对第二个不对(a+b-c)^2=[(a+b)-c]^2=(a+b)^2-2(a+b)c+c^2=a^2+b^2+2ab-2ac-2bc+c^2
x^2(y-z)+y^2(z-x)+z^2(x-y)=x^2y-x^2z+y^2z-y^2x+z^2x-z^2y=y(x^2-z^2)-xz(x-z)-y^2(x-z)=y(x+z)(x-z)-xz(
二重积分,投影面实在xoy上,但此圆柱面在xoy上的投影只是一个圈(不包含内部),估面积为零
解题思路:同学你好,本题利用圆心到直线的距离公式求解,具体过程见解析解题过程:
第二个分母写错了?(y-x)(z-x)/(x-2y+z)/(x+y-2z)+(z-y)(x-y)/(x+y-2z)/(y+z-2x)+(x-z)(y-z)/(y+z-2x)/(x-2y+z)=1
(y+z-x)/{x^2-(y+z)^2}=(y+z-x)/[(x-y-z)(x+y+z)]=-(x-y-z)/[(x-y-z)(x+y+z)]=-1/(x+y+z)
=x²(y-z)+y²(z-x)+z²(x-z+z-y)=(y-z)(x²-z²)+(z-x)(y²-z²)=(y-z)(x-z)
x^4(y-z)+y^4(z-x)+z^4(x-y)=xy(x^3-y^3)+yz(y^3-z^3)+zx(z^3-x^3)=xy(x^3-y^3)+yz(y^3-z^3)-zx[(x^3-y^3)+
FF指阀门与管线的连接形式的一种FF即FlatFace,是一种常见的平面法兰连接形式再问:但是这个球阀是螺纹连接的,还有可能是其他解释吗?是饮用水系统用的黄铜球阀再答:抱歉,螺纹连接都是小口径DN80
根据公式(a+b+c)^2=a^2+b^2+c^2+2ab+2bc+2ac公式展开:得到(x^2+y^2+z^2=2xy-2yz-2xz)-(x^2+y^2+z^2-2xy-2yz+2xz)合并同类项