Question

Resolvam pra mim esses sistemas de equação ... Pfv !!!

A) x+y=9
X-y=5

B)4x-y=8
X+y=7

C)x-3y=5
2x+4y=0

Answer 1

Letra a :

x+y=9
x-y=5
2x = 14
x = 14/2
x = 7

x + y = 9
7 + y = 9
y = 9 - 7
y = 2

Letra b :

4x-y=8
  x+y=7
5x    = 15
x = 15 / 5
x = 3

x + y = 7
3 + y = 7
y = 7 - 3
y = 4

Letra c :

  x-3y=5    .(2)
2x+4y=0   .(-1)

2x - 6y = 10
-2x -4y =   0
      10y = 10
y = 10/10
y = 1

x - 3y = 5
x - 3.1 = 5
x - 3 = 5
x = 5 + 3
x = 8