Question

Rezolvați prin metoda substituției vă rog dau coroană ​

Answer 1

c)

$\begin{cases}4x-3y=20 \\5x+2y=2 \end{cases}$

$5x = 2 - 2y \iff x = \dfrac{2 - 2y}{5}$

$\dfrac{4(2 - 2y)}{5}-3y=20$

$4(2 - 2y)-15y=100$

$8 - 8y-15y=100$

$23y = -92 \implies y = - 4$

$x = \dfrac{2 - 2(-4)}{5} = \dfrac{2 + 8}{5} = \dfrac{10}{5}$

$\implies x = 2$

$R: \bf x = 2;y = - 4$

d)

$\begin{cases}6x-2y=-14 \\7x+y=-13 \end{cases}$

$7x+y=-13 \iff y =-7x-13$

$6x-2(-7x-13)=-14 \iff 6x+14x+26=-14$

$20x+26=-14-26 \iff 20x = -40 \implies x = -2$

$y =-7(-2)-13 = 14-13 \implies y = 1$

$R: \bf x = -2;y = 1$