Question

НАЙДИТЕ ЗНАЧЕНИЕ ВЫРАЖЕНИЙ
(a+3b)^2-a^2-9b^2+4, если ab= -5
2. 16a^2 - (4a-7b)^2 + 49b^2 + 12, если ab = -2
3. (6a + b)^2 - (6a-b)^2 + 11, если ab = 5
4. (5n - 4)(5n + 4) - (5n + 4)^2(5n - 4)(5n +4) -(5n + 4)^2 при n=9.
РАДИ ХРИСТА РАСПИШИТЕ ПОПОДРОБНЕЕ

Answer 1

1.

${(a + 3b)}^{2} - {a}^{2} - 9 {b}^{2} + 4 = {a}^{2} + 6ab + 9 {b}^{2} - {a}^{2} - 9 {b}^{2} + 4 = 6ab + 4 = 6 \times ( - 5) + 4 = - 30 + 4 = - 26$

2.

$16 {a}^{2} - {(4a - 7b)}^{2} + 49 {b}^{2} + 12 = 16 {a}^{2} - 16 {a}^{2} + 56ab - 49 {b}^{2} + 49 {b}^{2} + 12 = 56ab + 12 = 56 \times ( - 2) + 12 = - 112 + 12 = - 100$

3.

${(6a + b)}^{2} - {(6a - b)}^{2} + 11 = 36 {a}^{2} + 12ab + {b}^{2} - 36 {a}^{2} + 12ab - {b}^{2} + 11 = 24ab + 11 = 24 \times 5 + 11 = 131$