Log Equations?

1) [log(x+1)^2]－log(x+1)^2=8
Sol
y=log(x+1)
y^2－2y－8=0
(y-4)(y+2)=0
y=4 or y=－2
(1) y=4
log(x+1)=4
x+1=10^4=10000
x=9999………….
(2) y=－2
log(x+1)=－2
x+1=10^(－2)=0.01
x=－0.99…………..
2) [log(3x－11)]^2－3log(3x－11)log(x－5)+2[log(x－5)]^2 =0
Sol
x=log(3x-11)，y=log(x-5)
x^2－3xy+2y^2=0
(x－y)(x－2y)=0
x=y or x=2y
(1) x=y
log(3x－11)=log(x－5)
3x－11=x－5
2x=6
x=3
3*3－11<0(不合)
(2) x=2y
log(3x－11)=2log(x－5)
3x－11=(x－5)^2
3x－11=x^2－10x+25
x^2－13x+36=0
(x－4)(x－9)=0
x=4(不合) or x=9…………