Question

Решите неравенство $lg^{2} x-2lgx-3 textless 0$

Answer 1

a=lgx, a²-2a-3<0
D/4=1+3=4    -1<a<3
a1=(1-2)/1=-1, lgx=-1, x=10^(-1)=0.1
a2=1+2=3, lgx=3,  x=10³=1000
x∈(0.1; 1000)