Question

sistema pelo método da substituição ..

( b
{ 4x+y= 0
{ x+5y= - 19

( c
{ - 2×-3y= - 9
{ x+4y= 12

Answer 1

4x+y= 0
x+5y= - 19

4x+y= 0
4x = -y
x = -y / 4
x = -0.25y

x+5y= - 19
-0.25 +5y = -19
4,75y = -19
y = -19 / 4,75
y = -4

4x+y= 0
4x +( -4) = 0
4x - 4 = 0
4x = 4
x = 4/4
x = 1

S{ 1 e -4}

( c
-2x-3y= - 9
x+4y= 12

x+4y= 12
x + y = 12 /4
x + y = 3
x = 3 - y

-2x-3y= - 9
-2 ( 3 -y) - 3y = -9
-6 + 2y -3y = -9
-y = -9 + 6
-y = -3
y = -3 /-1
y = 3

x+4y= 12
x + 4*3 = 12
x + 12 = 12
x = 12 - 12
x = 0

S{ 0 e 3 }

Answer 2

( b
{ 4x+y= 0(-5)
{ x+5y= - 19

-20x-5y= 0
x+5y= - 19
-19x = - 19(-1) ==> 19x = 19 ==> x = 1

5y = - 19 - x ==> 5y = - 19 - 1 ==> 5y = - 20 ==> y = - 4
========================================================
( c
{ - 2x - 3y = - 9
{    x + 4y = 12(2)

 - 2x - 3y = - 9
   2x + 8y = 24
           5y = 15 ==> y = 3
 
x = 12 - 4y ==> x = 12 - 4(3) ==> x = 12 - 12 ==> x = 0