Question

Помогите решить на фото и вот ,
3х +4у = 0
2х + 3у = 1

И

7u + 2v =1
17u +6v + -9

7 класс.

Answer 1

$3x + 4y = 0 \\ 2x + 3y = 1 \\ x = - \frac{4}{3} y \\ 2( - \frac{4}{3} y) + 3y = 1 \\ 3y - \frac{8}{3} y = 1 \\ \frac{1}{3} y = 1 \\ y = 3 \\ x = - \frac{4}{3} y = - \frac{4 \times 3}{3} = - 4 \\ = = = = = = = = = \\ 7x + 2y = 1 \\ 17x + 6y = - 9 \\ y = \frac{1 - 7x}{2} \\ 17x + 6( \frac{1 - 7x}{2} ) = - 9 \\ 17x + 3 - 21x = - 9 \\ 4x = 6 \\ x = 1.5 \\ y = \frac{1 - 7x}{2} = \frac{1 - 10.5}{2} = - 4.75 \\ ========= \\ 2x(2x + 3y) - {(x + y)}^{2} = 4 {x}^{2} + 6xy - {x}^{2} - 2xy - {y}^{2} = 3 {x}^{2} + 4xy - {y}^{2}$