svetazuna 1.
9 - 7(х+3) = 5 - 6х,
9 - 7х - 21 = 5 - 6х,
-7х + 6х = 5 - 9 + 21,
-х = 17,
х = -17,

2.
(х+3)/2 - (х-4)/7 = 1,
7(х+3) - 2(х-4) = 14,
7х + 21 - 2х + 8 = 14,
7х - 2х = 14 - 21 - 8,
5х = -15,
х = -3,

3.
(х+7)² - (х-2)² = 15,
х² + 14х + 49 - х² + 4х - 4 = 15,
14х + 4х = 15 - 49 + 4,
18х = -30,
х = -1 2/3,

4.
5х - 2 = 3(3х-1) - 4х - 4,
5х - 2 = 9х - 3 - 4х - 4,
5х - 9х + 4х = -3 - 4 + 2,
0х = -5,
уравнение не имеет решений,

5.
6х + (х-2)(х+2) = (х+3)² - 13,
6х + х² - 4 = х² + 6х + 9 - 13,
6х + х² - х² - 6х = 9 - 13 + 4,
0х = 0,
уравнение не имеет решений,

6.
(х+6)(х-1) - (х+3)(х-4) = 5х,
х² - х + 6х - 6 - х² + 4х - 3х + 12 = 5х,
х² - х + 6х - х² + 4х - 3х - 5х = 6 - 12,
х = -6