已知方程组2X﹢3Y=2K﹢1 3X﹣2Y=4K﹢3的解X,Y的和是6,求K的值-搜答案-神马作文网

3x-y=2k-1(1)4x+2y=k(2)(1)×2+(2)10x=5k-2x=(5k-2)/10(2)×3-(1)×410y=-5k+4y=(-5k+4)/10x-y=(5k-2+5k-4)/10

x+2y=4k(1)2x+y=2k+1(2)(2)-(1)x-y=-2k+1所以-1

2X=3Y①和3X+4Y=2K+1,②满足方程X+Y=3,③由①,③解得x=9/5,y=6/5,代入②,2k+1=51/5,k=23/5.

解方程组｛x+2y=k｛2x+3y=3k-1得x＝3k-2y＝1-k因为,x和y的和等于6所以,3k-2+1-k=6即,2k＝7所以,k＝7/2

1.用代入法：2x+3y=k3x-4y=k+11由x+y=3知x=3-y,代入上面两个式子中,得6-2y+3y=k得到y=k-6代入下面式子中9-3y-4y=k+11得9-7k+42=k+11得k=5

x+4y=1;x=1-4y;即x=1-4y=1+y;y=0;x=1;3x+2y=k=3

2x+3y=k1式3x+5y=k+12式1式乘以3,得6x+9y=3k3式2式乘以2,得6x+10y=2k+24式4式减去3式,得y=2-k将y=2-k代入1式,得x=(k-3y)/2=(k-6+3k

2x+3y=k①3x+5y=k+1②①x3,得6x+9y=3k③②x2,得6x+10y=2k+2④④-③,得y=2-k将y=2-k带入①,得2x+3(2-k)=k2x+6-3k=k2x=4k-6x=2

3x-2y=5(1)kx+(k-1)y=7(2)(2)*5-(1)5kx+(5k-5)y-3x+2y=35-5(5k-3)x+(5k-3)y=30x+y=1所以(5k-3)x+(5k-3)y=5k-3

2x-y=1+k①x+y=1-k②①＋②,得3x=2x=2/3又因为x=2y所以y=1/3从而k=2x-y-1=4/3-1/3-1=0再问：确定不再答：不谢

2x+3y=1-k……①3x-2y=2k……②两个方程相加得,5x+y=1+k,∴y=-5x+k+1……③得人方程①得,2x-15x+3k+3=1-k,解得x=(4k+2)/13得人③得,y=(-7k

等会再问：速度再答：再答：求采纳

2x-y=3kx+3y=2k解得x=-ky=k代入得-k+2k=1/2k=1/2

2x+3y=k3x+5y=k+1的解的和是-12,求k的值.6x+9y=3k6x+10y=2k+2y=2-kx=2k-32-k+2k-3=-12k=-11

x+2y=3ky-3x=-2解方程组得x=(3k+4)/7y=(9k-2)/7因为y＞-1且x＜1(9k-2)/7＞-1(3k+4)/7＜1-5/9

3x+2y=k+14x+3y=k-19x+6y=3k+38x+6y=2k-2相减得x=k+5代入3x+2y=k+1得3(k+5)+2y=k+1所以y=-k-7所以方程组的解是{x=k+5,y=-k-7

3x-2y=5①x+y=1②①+2*②=》5x=7=>x=7/5=>y=-2/5代入kx+(k-1)y=87k/5-2/5k+2/5=8=>k=38/5再问：跟我算的一样！

x=1/4+k/4y=1/4-7k/4x+y=1/2-3k/21/3

由两式消去x或y得：①7y=13－4k,∴k=（13－7y）／4,代人0≤k≤1∴9／7≤y≤13／7,②7x=23＋k∴k=7x－23∴23／7≤x≤24／7

x+2y=3x+y=1解此方程组得:x=-1y=2把x=-1,y=2代入2x-y=k得:2×(-1)-2=kk=-4