Помогите с логарифмами 1 и 2 решены Помогите с остальными

3
-3<x<7
1(3+x)=7-x
2x=4
x=2

4
x>-15
log(3)(x+15)=t
4t^2=16t
4t(t-4)=0
t1=0
t2=4
log(3)(x+15)=0
x+15=1
x1=-14

log(3)(x+15)=4
x+15=81
x2=66

7)
(log2 x^2)^2 = 16*log2 8x - 60 ---> ОДЗ: x > 0
__ (log2 x^2)^2 = (2*log2 x)^2 = 4*(log2 x)^2
__ 16*log2 8x = 16*(log2 8 + log2 x) = 16*(log2 2^3 + log2 x) =
= 16*(3 + log2 x) = 48 + 16*log2 x
=>
4*(log2 x) = 48 + 16*log2 x - 60 ---> (:) на 4 и log2 x = t
t^2 = 12 + 4t
t^2 - 4t - 12 = 0 ----> t1 = -2; t2 = 6
log2 x = t1 = -2 ---> x1 = 2^(-2) = 1\4
log2 x = t2 = 6 ---> x2 = 2^6 = 64
6)
log2 (x-1) - 2 = log2 (3x-7) - log2 (x+1)
ОДЗ:
{ (x-1) > 0 ---> { x > 1
{(3x-7) > 0 ---> { x > 7\3
{ (x+1) > 0 ---> { x > -1
Общее ОДЗ: x > 7\3
=>
log2 (x-1) - log2 2^2 = log2 (3x-7) - log2 (x+1)
log2 {(x-1)/4} = log2 {(3x-7)/(x+1)}
(x-1)/4 = (3x-7)/(x+1)
x^2 - 1 = 12x - 28
x^2 - 12x + 27 = 0 --->
x1 = 3 - не удовлетв. ОДЗ;
x2 = 9 <--- ответ

5) решить квадраттное уравнение с заменой log9 (x-6) = t (ОДЗ: x > 6)