1.
1)
38² - 64 = 38² - 8² = (38 - 8)(38 +8) = 30 * 46 = 1380,
2.
1)
2в² - 18 = 2 * (в² - 9) = 2 * (в - 3)(в + 3),
3)
81х² - 18ху + у² + 63х - 7у = (81х² - 18ху + у²) + (63х - 7у) =
= (9х - у)² + 7*(9х - у) = (9х - у)(9х - у + 7),
4)
m² + n² + 2mn = (m + n)².
3.
а)
(8 - 2n)(8 + 2n) + (9 + 2n)² - 64 = 64 - 4n² + 81 + 36n + 4n² - 64 =
= 36n + 81 = 9(4n + 9),
б)
(3х - 8)² + (4х - 8)(4х + 8) = 9х² - 48х + 64 + 16х² - 64 = 25х² - 48х,
при х=-2:
25 * (-2)² - 48 * (-2) = 100 + 96 = 196,
4.
1 число - х,
2 число - (х+2),
(х+2)² - х² = 188,
х² + 4х + 4 - х² = 188,
4х = 184,
х = 46 - 1 число,
х+2 = 46+2 = 48 - 2 число
1) 18 - 16х = -30х - 10, 2) -7х + 2 = 3х - 1, 3) 10 - 2х = 12 - х,
-16х + 30х = -10 - 18, -7х - 3х = -1 - 2, -2х + х = 12 - 10,
14х = -28, -10х = -3, -х = 2,
х = -28 : 14, х = -3 : (-10), х = -2;
х = -2; х = 0,3;
4) 6х - 19 = -2х - 15, 5) 0,2х + 3,4 = 0,6х - 2,6, 6) 5/6х + 12 = 1/4х - 2,
6х + 2х = -15 + 19, 0,2х - 0,6х = -2,6 - 3,4, 12(5/6х + 12) = 12(1/4х - 2),
8х = 4, -0,4х = -6, 10х + 144 = 3х - 24,
х = 4 : 8, х = -6 : (-0,4), 10х - 3х = -24 - 144,
х = 0,5; х = 15; 7х = -168,
х = -168 : 7,
х = -24.