log急需急需

1. /x-4y/+（2y—1)^2=0,==>x=4y, 2y-1=0=>x=2,y=1/2
log2(y/x)= log2(1/4)= -2

2. 2lg[(x-y)/2]=lgx+lgy=lgxy,
[(x-y)/2]^2=xy, x^2+y^2-6xy=0
(x/y)^2+1-6x/y=0
x/y =2。（-3舍）

3. lg[3(x^3)]-lg[3(y^3)]=9,
lg[3(x^3)/3(y^3)]=9=lg10^9
(x/y)^3 =10^9
x/y=10^3=1000

4. log2(x)+log2(y)=0==>log2(xy)=0==>xy=1
x^4+y^4=194,==>(x^2+y^2)^2-2x^2y^2=194
==>x^2+y^2=14=(x+y)^2-2xy
==>x+y=4
log2(x+y)=log2(4)=2

lg[3(x^3)]-lg[3(y^3)]=lg[3(x^3)/3(y^3)]=3lg(x/y)=9,x/y=10^3

(1)x=4y,2y-1=0
x=2,y=1,
log2(y/x)=0
(2)(x-y/2)^2=xy
x/y=3+_2倍根号2
(3)x/y=1
(4)4xy=0,
x=0/y=0
log2(x+y)=2.5log2+0.25log3

x=2,y=1/2
[(x-y)/2]^2=xy
x/y=1000
2

1、|x-4y|=0且2y-1=0，得x=2、y=1/2带入可得，

2、（x-y)^2=4xy,得x/y+y/x=6,t^2-6t+1=0 (设t=x/y) 可得

(t-2)(t+3)=0得t=2(因为x>0