已知y 1与x 3成正比例,并且x=1时,y=8

设,y=k/x+a/x,然后分别把两个值带入,解方程组k=xy=-2,和交点带入第二个式子求m,再联立解方程组.

题写得不清楚再问：哪里再答：设Y1=kx²,y2=g(x-2)代入得12=3kx²+g(x-2)=12k-4g3=3/4k-5/2g推得12=3k-10g求出k=2/3和g=-1代

∵y1与3x成正比例y2与（x+5）成正比例∵y1=k1×3xy2=k2(x+5)（k1k2≠0）∵y=2y1-y2=6k1-k2（x+5）∴12=6k1-6k2-2=-6k1-4k2∴k1=1k2=

y1=m(x+1)y2=nx*x且y=y1+y2;当x=1,y=2时（将x=1,y=2代入式子中）y=y1+y2得到2=2m+n当x=0,y=2时y=y1+y2得到2=m+0m=2,n=-2所以y=2

y1与x成反比例,y2与(x-2)成正比例所以y1=k/x,y2=m(x-2)所以y=k/x-m(x-2)x=3时,y=5x=1时,y=-1代入5=k/3-m-1=k+m所以k=3,m=-4所以y=3

y1与x成反比例:y1=n/xy2与x-2成正比例:y2=m(x-2)并且当x=3时,y=5:y=y1-y2=n/x-m(x-2)=n/3-m(3-2)=n/3-m=5当x=1时,y=-1:y=y1-

y=k1/x-k2*(x-2),5=k1/3-k2,-1=k1+k2.k1=3,k2=-4.y=3/x+4(x-2)

设Y1=K1X,Y2=K2X^2∴Y=3K1X-K2X^2,得方程组：-2=6K1-4K2-9=9K1-9K2化简得：3K1-2K2=-1K1-K2=-1解得：K1=1,K2=2∴Y=3X-2X^2再

设y1=k1/x,y2=k2*(x-2),y=k1/x+k2*(x-2),x=3时,y=5,所以5=k1/3+k2,当x=1时,y=-1,所以-1=k1-k2,解得k1=3,k2=4,所以y=3/x+

y1与X的平方成正比例y1=k1xy2与X成反比例y2=k2/x则y=k1x+k2/x当x=1时k1+k2=11当x=3时3k1+k2/3=-179k1+k2=-5122式减1式得8k1=-52k1=

设y1=k1(x-1),y2=k2(2x+3)所以y=k1(x-1)+k2(2x+3)（1,-1）,（3,2）代入上式得：k1=1.7,k2=-0.2y=1.3x-2.3

因为y1与x的平方成反比例,不妨设y1=k/x^2；y2与x+2成正比例,不妨设y2=k'(x+2).y=y1-y2=k/x^2-k'(x+2)——解释一下y等于x平方分之k,再减去k倍的x加2根据x

设y1=2mx,y2=n(x+1),(m,n均为常数,m≠0,n≠0),则y=2mx+n(x+1)分别把x=1,y=2;x=-2,y=3代入y=2mx+n(x+1)得关于m,n的方程组：2=2m+2n

因为Y1与X+1成反比例,设为a/Y1=X+1,即Y1=a/(X+1)Y2与X²成正比例,设为Y2=bX²Y=Y1+Y2=a/(X+1)+bX²当X=0,Y=a/（0+1

由题意,不妨设：y1=k*根号x,y2=m/x²那么：y=y1+y2=k*根号x+m/x²已知当x=1时,y=-12；当x=4时,y=7,则有：{k+m=-12(1){2k+m/1

设y1=k1*√x,y2=k2*(1/x^2);x=1时,y=y1+y2=k1+k2=11x=4时,y=y1+y2=2*k1+k2/16=6.5解得k1=3,k2=8y=3*√x+8/x^2x=9时,

设y1=axy2=b/x²Y=Y1+Y2=ax+b/x²当x=22a+b/4=19当x=33a+b/9=19解得a=5,b=36所以y=5x+36/x²

设y1=k/xy2=kx^2因为当x=1时,y=2,x=2时,y=4又1/2所以可以算出k=2,k=1所以y1=2/xy2=x^2所以y=2/x+x^2

1.y1=k1/(x+3)y2=k2*(-3x)y=k1/(x+3)+k2(-3x)把x=1,y=-1.5,x=-1y=0代入,解得k1=-2k2=1/3y=-2/(x+3)-x当x=3,y=-10/

Y=Y1+Y2=k1x+K2/X函数Y=Y1+Y2的图象过点(1,2)和(2,1/2),K1+K2=22K1+K2/2=1/2K1=-1/3K2=7/318K1+5K2=_17/3_____