31,若2x+5y+4z=6,3x+y-7z=-4,那么x+y-z的值是多少?
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(1)2x+3y-4z=-5(2)x+y+z=6(两边同时×33x+3y+3z=18(与(1)相减得(5)(3)x-y+3z=10(与(2)相加得(4))(4)2x+4z=16(5)x+7z=23(两
(5x+3y+2z)+(4x+6y+7z)=2011+20129(x+y+z)=4023x+y+z=447
设x/3=y/4=z/5=m则x=3m,y=4m,z=5m则x+y+z/3x-2y+z=(3m+4m+5m)/(9m-8m+5m)=12/6=2
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
1)2x+z=3,8x+4z=123x+y-z=8,9x+3y-3z=24x+3y+2z=38x-5z=21,9z=-9,z=-1,x=2,y=12)5x+2y-3z=2x+2y+z=6,4x-4z=
x+y-z=6,①x-3y+2z=1,②3x+2y-z=-7③①-②得4y-3z=5④①*3-③得y-2z=25⑤④-⑤*4得5z=-95z=-19代入⑤得y+38=25y=-13代入①得x-13+1
因为x:y:z=3:4:5所以设x=3k,y=4k,z=5k(k≠0)(1)z/(x+y)=5k/(3k+4k)=5k/7k=5/7(2)x+y+z=63k+4k+5k=612k=6k=1/2x=3k
题打错了吧,应该是x+y-z吧?要不算不出来.你看一下: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-
2x+5y+4z=6(1)3x+y-7z=-4(2)(2)-(1)得到式(3)(1)-(3)得到式(4)(4)-(3)得到一个只有y和z的等式,你解出y(用z表示的式子)把y的表达式代入(1),解出x
x+y+z=41式x+y+2z=52式3x+y-z=63式2-1式z=13-2式2x-3z=14式z=1代入4式x=2再代入1式y=1∴x=2,y=1,z=1请点击下面的【选为满意回答】按钮,再问:�
2x+y+z=10(1)x+2y+z=-6(2)x+y+z=8(3)(2)-(3):y=-14(4)(1)-(2):x-y=16(5)把(4)代入(5):x+14=16x=2(6)把(4)和(6)代入
已知,2x+5y+4z=6,3x+y-7z=-4,可得:2(2x+5y+4z)+3(3x+y-7z)=2*6+3*(-4)=0;即有:13(x+y-z)=0,所以,x+y-z=0.
/>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
把z=2x+y代入4x=7y+5Z得4x=7y+10x+5yx=-2y,z=-3yx:y:z=-2:1:-3
题目设置挺好的不会很变态,没什么难度由4x-3y-6z=0,x+2y-7z=0,可以解得x=3z,y=2z,将它代入代数式5x*5x+2y*2y-z*z/2x*2x-3y*3y-10z*10z=(25
第一道设x/4=y/5=z/6=k,则x=4k,y=5k,z=6k,代入2x+3y-4z=-3得8k+15k-24k=-3,k=3.第二道1/x+y-1/x-y=-3/20(1),2/x+y+3/y-
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+
3x+5y+6z=5,4x+2y+z=2将以上两式相加得:7x+7y+7z=7所以x+y+z=1再问:明白了!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
由题意得3x+5y+6z=54x+2y+z=2,两式相加的:7x+7y+7z=7∴x+y+z=1.故选B.
x:y:z=3:4:5=6,求x-y+z分之x+y-z的值3y=4x,y=4x/3,3z=5x,z=5x/3x-y+z分之x+y-z=(x-4x/3+5x/3)/(x+4x/3-5x/3)=(4x/3