Question

Resolva os sistemas pelo Método da Substituição
B; 4x + y = 0
X+5y= -19

C; -2x - 3y = -9
X + 4y =12

D; -6x + 2x =8
9x - y = 8
MeAjudem ,

Answer 1

B) 4x + y = 0 e x + 5y = - 19
4x + y = 0
y = - 4x

x + 5y = - 19
x + 5(- 4x) = - 19
x - 20x = - 19
- 19x = - 19
x = -19/-19
x = 1

y = - 4x
y = - 4×1
y = - 4



C) - 2x - 3y = - 9 e x + 4y = 12
x + 4y = 12
x = 12 - 4y

- 2x - 3y = - 9
- 2(12 - 4y) - 3y = - 9
- 24 + 8y - 3y = - 9
5y = - 9 + 24
5y = 15
y = 15/5
y = 3 

x = 12 - 4y
x = 12 - 4×3
x = 12 - 12
x = 0



D) - 6x + 2y = 8 e 9x - y = 8
9x - y = 8
- y = 8 - 9x
y = - 8 + 9x

- 6x + 2y = 8
- 6x + 2(- 8 + 9x) = 8
- 6x - 16 + 18x = 8
12x = 8 + 16
12x = 24
x = 24/12
x = 2

y = - 8 + 9x
y = - 8 + 9×2
y = - 8 + 18
y = 10
 

Answer 2

B; 4x + y = 0  ==> Y = - 4x ==> y -4(1) ==> Y = - 4
X+5y= -19 

x + 5(-4x) = - 19 => x - 20x = - 19 => - 19x = -19(-1) => 19x =19 => x = 1
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C; -2x - 3y = -9
X + 4y =12 ==> x = 12 - 4y ==> x= 12 - 4(3) ==>x= 12 -12 == x = 0

-2(12 - 4y) - 3y = -9 => - 24 + 8y - 3y = - 9 => 5y = -9+ 24 => 5y=15 ==> y =3
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D; -6x + 2x =8 
9x - y = 8  ==> y = 9x - 8==> y = 9.(-2) - 8 ==> y= -18-8==> y = - 26

-6x + 2x =8 ==> - 4x = 8(-1)==> 4x = - 8 ==> x = - 2