Question

qual o valor do x e y:
a) x+2y=5 2x-3y=4

Answer 1

Boa noite!

Solução!

Vou resolver pelo método da adição.

$\begin{cases} x+2y=5\\ 2x-3y=4 \end{cases}\\\\\\\\\ \begin{cases} x+2y=5.(-2)\\ 2x-3y=4 \end{cases}\\\\\\\\\ \begin{cases} -2x-4y=-10\\ ~~2x-3y=4 \end{cases}\\\\\\ -4y-3y=-10+4\\\\\ -7y=-6\\\\\\ y= \dfrac{-6}{-7}\\\\\\ \boxed{y= \dfrac{6}{7}}$




$x+2y=5\\\\\ x+2( \frac{6}{7}) =5\\\\\ x+ \frac{12}{7} =5\\\\\ 7x+12=35\\\\\ 7x=35-12\\\\\ 7x=23\\\\ \boxed{x= \frac{23}{7}}$



$\boxed {Resposta:S=\{\frac{23}{7},\dfrac{6}{7}\}}$

Boa noite!
Bons estudos!

Answer 2

x + 2y = 5     (-2)
2x - 3y = 4

- 2x - 4y = - 10
  2x - 3y = 4  (+)
--------------------
     - 7y = - 6  (-1)
   7y = 6
y = 6/7

x + 2y = 5
x + 2. 6  = 5
         ---
          7

7x + 12 =  35
----------    -----
     7           7

7x = 35 - 12
7x = 23
x = 23/7