Объяснение:

[tex]1)3 {x}^{4} - 12 {x}^{2} + 18x \\ 2)2 {x}^{2} + x - 6x - 3 = 2 {x}^{2} - 5x - 3 \\ 3)20 {a}^{2} + 24ab - 35ab - 42 {b}^{2} = 20 {a}^{2} - 11ab - 42 {b}^{2} \\ 4) {y}^{3} + {y}^{2} - 8y + 2 {y}^{2} + 2y - 16 = {y}^{3} + 3 {y}^{2} - 6y - 16 \\ 2.1)5a(a - 4b) \\ 2)7 {x}^{3} (1 - 2 {x}^{2} ) \\ 3)3(a - b) + x(a - b) = (a - b)(3 + x) \\ 3.4 {x}^{2} - 12x = 0 \\ 4x(x - 3) = 0 \\ 4x = 0 \\ x - 3 = 0 \\ x = 0 \: or \: x = 3 \\ 4.6 { a}^{2} - 10a - ( {a}^{2} - 7a - 3a + 21) = 6 {a}^{2} - 10a - {a}^{2} + 7a + 3a - 21 = 5 {a}^{2} - 21[/tex]