Ас^4-c^4-ac^2+c^2=<span>C^4 (a-1) + c^2(a-1) = (a-1) c^2 (C^2-1) = C^2(a-1) (c-1)(c+1)</span>
1/27=1/3^3=3^-3
3^3x+1 >3^-3
Основания больше 1
3х+1> -3
3х> -3 -1
3х> -4
Х> -4/3
/////////////////
-------(-4/3)----------------
Х€(-4/3; +~)
Х> 2+7
x< 50/5
x> 9
x< 10
9 < x < 10
х (9; 10)
1) log7(x^2-2x-8)=log7(7)
x^2-2x-8=7
x^2-2x-15=0
D=64
x1=5
x2=-3
2) log1/2(x^2-4x-5)>log1/2(16)
ОДЗ:x^2-4x-5>0
D=36
x1=5
x2=-1
Снимаем логарифм:
x^2-4x-5<16
x^2-4x-21<0
D=100
x1=7
x2=-3
x=(5;7)