Question

решите уравнения lg (x-1)+lg (x+1)=0

Answer 1

lg (x-1)+lg (x+1)=0
x+1>0
x-1>0
log(x-1)+log(x+1)=0
x>-1
x>1
log(x-1)+log(x+1)=0
x>1
log(x-1)+log(x+1)=0
x>1
(x-1)(x+1)=1
x>1
x=-√2
отв:x=√2