Question

Помогите log(3x+1)+log10x=1

Answer 1

lg(3x +1) + lg(x) = 1  ОДЗ: x> 0
lg(3x+1)*(x) = 1
3x^2 + x = 10^1
3x^2 + x - 10 = 0   
D = 1+ 4*3*10 = 121
x1 (-1 - 11)/6
x1 = -2 не удовлетворяет ОДЗ
x2 = (-1 + 11)/6
x2 = 5/3
х2 = 1(2/3)
Ответ: х = 1(2/3)