Question

Resolva os sistemas :

A) x-y=4 B)2x+3y=3 C)x+2y=18
3x-6y-3 x+4y=-1 3x+4y=14

Answer 1

a) x - y = 4 e 3x - 6y = 3

x-y = 4
x = 4 + y

3x-6y = 3 (Simplifique)
x - 2y = 1
(4+y) - 2y = 1
4 + y - 2y = 1
4 - y  = 1
-y = 1 - 4
-y = -3
y = 3

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

b) 2x + 3y = 3 e x+4y = -1

x + 4y = -1
x = -1 - 4y

2x + 3y = 3
2(-1-4y) + 3y = 3
-2 - 8y + 3y = 3
-8y + 3y = 3+2
-5y = 5
y = -5/5
y = -1

x = -1 - 4y
x = -1 - 4(-1)
x = -1 + 4
x = 3

c) x+2y = 18 e 3x+4y = 14

x+2y = 18
x = 18 - 2y

3x+4y = 14
3(18 - 2y) + 4y = 14
54 - 6y + 4y = 14
54 - 2y = 14
-2y = 14 - 54
-2y = -40
y = 40/2
y = 20

x = 18 - 2y
x = 18 - 2.20
x = 18 - 40
x = -22