已知X^20Y^15Z^5=32求X^8Y^6Z^2的值
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5x+3y=3z--------a-x-3y=-z--------ba式+b式4x=2z得z=2x代入a中得x=3y,y=x/3x:y:z=x:x/3:2x=1:1/3:2=3:1:6
x:y:z=(3y/5):y:(7y/4)=(3/5):1:(7/4)=12:20:35再问:已知x+2y-z=02x+3y+z=0求x:y
(1)因为2x+3y-4z=7(1)3x-2y+z=3(2)x+5y+9z=20(3)(1)+(2)+(3)得(2x+3y-4z)+(3x-2y+z)+(x+5y+9z)=7+3+20整理得:6x+6
x=4y/3y=yz=2y/5所以,x:y:z=4/3:1:2/5=20:15:6
由x+y-z=0,2x-y+2z=0可得:z=-3xy=-4x则3x-2y+5z/5x-3y+2z=3x+8x-15x/5x+12x-6x=-4x/11x=-4/11
(x+2y)/3=(y+3z)/4(x+2y)/3=(z+5x)/5化简得4x+5y=9z-10x+10y=3z解得x=(5/6)zy=(17/15)zx:y=(5/6):(17/15)=25:34y
设:x/4=y/5=z/6=k则有:x=4k,y=5k,z=6k(x+y+z)/(3x-2y+z)=(4k+5k+6k)/(12k-10k+6k)=15k/8k=15/8
由题意得:x+y=3①y+z=4②x+z=5③①+②+③得:2x+2y+2z=12,即x+y+z=5.故选A.
x+4y+3z=3x-2y-5z=0则x+4y+3z=0①3x-2y-5z=0,则6x-4y-10z=0②①②两式相加,得7x-7z=0,所以x=z代入①,得z+4y+3z=0,所以y=-z所以x+2
4x-5y+2z=0(1)x+2y=3z(2)(2)×4-(1)得:13y=14zy=14/13z(1)×2+(2)×5得:13x=11zx=11/13z所以:x:y:z=11/13:14/13:1=
由于2x+5y+4z=15,7x+y+3z=14;令4x+y+2z=m(2x+5y+4z)+n(7x+y+3z)=(2m+7n)x+(5m+n)y+(4m+3n)z;由于左边=右边,则可列方程组2m+
2x+5y+4z=157x+y+3z=1442x+6y+18z=8444x+11y+22z=99所以4x+y+2z=9
用待定系数法4x+y+z=m(2x+5y+4z)+n(7x+y+3z)得到方程2m+7n=45m+n=14m+3n=1此方程组没有公共解说明由2x+5y+4z=157x+y+3z=14不能得到4x+y
设a(2x+5y+4z)+b(7x+y+3z)=x+y+z比较系数得2a+7b=5a+b=4a+3b=1a=1/11,b=2/11因此x+y+z=a(2x+5y+4z)+b(7x+y+3z)=1/11
/>x/4=y/5=z/6=t分别用t表示x,y,z然后带入到要求的式子x+y+z/3x-2y+z中最终解得结果
解法1:2x+5y+4z=0式①3x+y-7z=0式②x+y-z=?式③式①=0,式②=0,所以式①-式③=式②-式③即:2x+5y+4z-x-y+z=3x+y-7z-x-y+zx+4y+5z=2x+
X=3K,Y=4K,Z=5K3X+2Y-4Z=189K+8K-20K=18K=-6X=-18,Y=-24,Z=-30X+Y+Z=-72
两式相加,得6X-5Z=0即X=5Z/6,即X/Z=5/6.再将X=5Z/6代入式1,得5Y+11Z/2=0得Y/Z=-11/10
应该是3X=4Y,5Y=6Z吧?X+Y:Y+Z=[(4Y/3)+Y]:(Y+5Y/6)=14;11