Question

Помогите пжжжж 1,2,5

Answer 1

Объяснение:

номер 1: а)

$(a - 4)(a - 2) = {a}^{2} - 2a - 4a + 8 = {a}^{2} - 6a + 8$

б)

$(3x + 1)(5x - 6) = 15 {x}^{2} - 18x + 5x - 6 = 15 {x}^{2} - 13x - 6$

номер 2: а)

${(y - 4)}^{2} = {y}^{2} - 8y + 16$

б)

${(7x + a)}^{2} = 49 {x}^{2} + 14ax + {a}^{2}$

в)

$(5c + 2)(5c - 2) = {(5c)}^{2} - {2}^{2} = 25 {c}^{2} - 4$

г)

$(3a + 2b)(3a - 2b) = 9 {a}^{2} - 4 {b}^{2}$

номер 5:

$12 - {(4 - x)}^{2} = x(3 - x) \\ 12 - (16 - 8x + {x}^{2} ) = 3x - {x}^{2} \\ 12 - 16 + 8x - {x}^{2} - 3x + {x}^{2} = 0 \\ - 4 + 5x = 0 \\ 5x = 4 \\ x = 0.8$