log2(3-x) - log4(x+5) =1
log2(3-x)=1+log4(x+5)
log4 (3-x)²=log4 4(x+5)
(3-x)²=4(x+5)
x²-6x+9=4x+20
x²-10x-11=0
(x-11)(x+1)=0
x=11或x=-1
经检验,x=11是增根(不满足真数大于0)
所以 x=-1
log2(3-x) - log4(x+5) =1
log2(3-x)=1+log4(x+5)
log4 (3-x)²=log4 4(x+5)
(3-x)²=4(x+5)
x²-6x+9=4x+20
x²-10x-11=0
(x-11)(x+1)=0
x=11或x=-1
经检验,x=11是增根(不满足真数大于0)
所以 x=-1