已知z+xy+2y+求dz
樊胥鸦610已知XY+X/X+Y+1=2 XZ+2X/X+Z+2=3 (Y+1)(Z+2)/Y+Z+3=4 求X+Y+Z的值 -
台沾政13235264519 ______ (XY+X)/(X+Y+1)=2(x+y+1)/(xy+x)=1/2(x+y+1)/x(y+1)=1/21/(y+1)+1/x=1/2 同样得:1/(z+2)+1/x=1/31/(y+1)+1/(z+2)=1/4 解方程组得:1/x=7/24,1/(y+1)=5/24,1/(z+2)=1/24 所以 x=24/7,y=19/5,z=22 x+y+z=29又8/35
樊胥鸦610已知x+y:z=y+z:x=z+x:y,求(x+y)(y+z)(z+x):xyz的值 -
台沾政13235264519 ______ 1、 令k=(x+y)/z=(y+z)/x=(z+x)/y x+y=kz y+z=kx z+x=ky 相加2(x+y+z)=k(x+y+z)(k-2)(x+y+z)=0 k=2或x+y+z=0 x+y+z=0 则x+y=-z k=(x+y)/z=-1 所以k=2,k=-1 所以原式=[(x+y)/z]*[(y+z)/x]*[(z+x)/y]=k³=8或-1 2、(x-4y)(x+y)=0 x-4y=0,x+y=0 x=4y,x=-y 所以x:y=4或-1
樊胥鸦610已知(x²/z+y)+(y²/x+z)+(z²/x+y)=0 -
台沾政13235264519 ______ 令t=(x/z+y)+(y/x+z)+(z/x+y) 可得xt+yt+zt =(x^2/z+y)+(y^2/x+z)+(z^2/x+y)+x+y+z=0+x+y+z=x+y+z 即(x+y+z)t=x+y+z(x+y+z)(t-1)=0 t=1 (x/z+y)+(y/x+z)+(z/x+y)的值为1
樊胥鸦610x+y+z=10,xy+yz+zx=33,(y+z)(z+x)(x+y)=294,求X,Y,Z -
台沾政13235264519 ______ 已知x+y+z=10,xy+yz+zx=33,(y+z)(x+z)(x+y)=294,求x、y、z的 已知x+y+z=10①,xy+yz+zx=33②,(y+z)(x+z)(x+y)=294③,求x、y、z的 解:∵由①得y+z=10-x,x+z=10-y,x+y=10-z;一并代入③,得﹙10-x﹚﹙10-y﹚﹙10-z﹚=294④即10³-10²﹙x+y+z...
樊胥鸦610已知x+y+z=1,xy+yz+xz=0,求x^2+y^2+z^2的值. -
台沾政13235264519 ______[答案] (x+y+z)²=1² x²+y²+z²+2xy+2yz+2xz=1 x²+y²+z²+2(xy+yz+xz)=1 x²+y²+z²=1-2(xy+yz+xz)=1-0=1
樊胥鸦610已知速度场vx=2y+3z, vy=z+2x, vz=x+2y,求涡线方程 - 上学吧普...
台沾政13235264519 ______ y+z=5-x yz=3-xy-xz=3-x(y+z)=3-x(5-x)=x^2-5x+3 所以y和z是方程 a^2-(5-x)a+x^2-5x+3=0的两个跟 方程有解则判别式大于等于0(5-x)^2-4(x^2-5x+3)>=0 x^2-10x+25-4x^2+20x-12>=03x^2-10x-13<=0(x+1)(3x-13)<=0-1=x<=13/3
樊胥鸦610已知x+2y+3z=2,3x+y+2z=3,2z+3y+z=4,求x+y+z的值 -
台沾政13235264519 ______[答案] x+2y+3z=2,(1) 3x+y+2z=3,(2) 2x+3y+z=4 (3) (1)+(2)+(3)得 6(x+y+z)=9 得x+y+z=3/2
樊胥鸦610已知X+y+z=5 xy+yz+xz=3 求z最大最小 -
台沾政13235264519 ______ ∵x+y+z=5 ∴x+y=5-z ① ∵xy+yz+xz=3,即xy+z(x+y)=3 ∴xy=3-z(x+y)=3-z(5-z)=z²-5z+3 ② 由①②式,得:x、y是方程t²-(5-z)t+z²-5z+3=0的另个实数根 则:△=(5-z)²-4(z²-5z+3)=-3z²+10z+13≥0 即:3z²-10z-13≤0,(3z-13)(z+1)≤0 ∴-1≤z≤13/3 即z的最大值为13/3,最小值为-1
樊胥鸦610已知:x/2=y/ - 3=z/5,求:(x - 2y+3z)/(x+y - z)的值 -
台沾政13235264519 ______ 设x=2a,y=-3a,z=5a (x-2y+3z)/(x+y-z)=(2a+6a+15a)/(2a-3a-5a)=23a/-6a=-23/6