Question

Método de substituição
a) {x = 5y
{x + y = 12

b) {x - y = 10
{2x + 3y = 10

c) {x = y + 3
{4x + y = -3

d) {x + y = 3
{12x - 9y = -20


ME AJUDEM POR FAVOR!!!!

Answer 1

Resposta:

$\text{\sf Leia abaixo}$

Explicação passo-a-passo:

$\begin{cases}\sf x = 5y\\\sf x + y = 12\end{cases}$

$\sf 5y + y = 12$

$\sf 6y = 12$

$\boxed{\boxed{\sf y = 2}}$

$\sf x = 5 \times 2$

$\boxed{\boxed{\sf x = 10}}$

$\begin{cases}\sf x - y = 10\\\sf 2x + 3y = 10\end{cases}$

$\sf x = 10 + y$

$\sf 2(10 + y) + 3y = 10$

$\sf 20 + 2y + 3y = 10$

$\sf 20 + 5y = 10$

$\sf 5y = 10 - 20$

$\sf 5y = -10$

$\boxed{\boxed{\sf y = -2}}$

$\sf x = 10 + (-2)$

$\sf x = 10 - 2$

$\boxed{\boxed{\sf x = 8}}$

$\begin{cases}\sf x = y + 3\\\sf 4x + y = -3\end{cases}$

$\sf 4(y + 3) + y = -3$

$\sf 4y + 12 + y = -3$

$\sf 5y = -3 - 12$

$\sf 5y = -15$

$\boxed{\boxed{\sf y = -3}}$

$\sf x = -3 + 3$

$\boxed{\boxed{\sf x = 0}}$

$\begin{cases}\sf x + y = 3\\\sf 12x - 9y = -20\end{cases}$

$\sf x = 3 - y$

$\sf 12(3 - y) - 9y = -20$

$\sf 36 - 12y - 9y = -20$

$\sf -21y = -20-36$

$\sf 21y = 56$

$\boxed{\boxed{\sf y = \dfrac{8}{3}}}$

$\sf x = 3 - \dfrac{8}{3}$

$\sf x = \dfrac{9-8}{3}$

$\boxed{\boxed{\sf x = \dfrac{1}{3}}}$