Question

5) resolva o sistema a seguir
x + y = 12
3x - y = 20

6) resolva o sistema a seguir
3x + y = 24
5x + 2y = 60

Answer 1

Olá! :D

05:

$\underline{_{_{_{\large +}}} \begin{cases} \mathrm{x + \bcancel y = 12} \\ \mathrm{3x -\bcancel y = 20} \end{cases}} \\ \mathrm{ 4x = 32} \\ \color{orangered} \underline{\boxed{ \therefore \: \mathrm{ x = 8 }}}\\ \rightarrow \mathrm{x + y = 12} \\ \mathrm{ 8 + y = 12 }\\ \color{orangered}\underline{ \boxed{\therefore \: \mathrm{y = 4}}}$

$\rule{6.5cm}{.01mm}$

06:

$\underline{_{_{_{\large +}}} \begin{cases} \mathrm{3x + y = 24 \: \: \color{orangered}\cdot( - 2)} \\ \mathrm{5x + 2 y = 60} \end{cases}} \\\underline{_{_{_{\large +}}} \begin{cases} \mathrm{ - 6x - \cancel{ 2y} = - 48} \\ \mathrm{5x + \cancel{ 2y}= 60} \end{cases}} \\ \mathrm{ - x = 12} \\ \color{orangered} \underline{\boxed{ \therefore \mathrm{ x = -12 }}}\\ \Rightarrow \mathrm{5x +2y = 60} \\ \mathrm{ -60 + 2y = 60 }\\ \color{orangered}\underline{ \boxed{\therefore \mathrm{y = 60}}}$