Question

1) Resolva os sistemas pelo método da substituição.

a) {x + y = 4
{3x + y = 28


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

c) {-2x - 3y = -9
{ x+ 4y = 12

d) {-6x + 2y = 8
{9x - y = 8

Answer 1

A)
{x+y=4
{3x+y=28
X+y=4
X=4-y

3x+y=28
3.(4-y)+y=28
12-3y+y=28
-3y+y =28-12
-2y=16
2y=-16
Y=-16/2
Y=-8

X=4-(-8)
X=4+8
X=12

Answer 2

a) x=4-y
3(4-y)+y=28
12-3y+y=28
-2y=16
y=-8
x=4-(-8)
x=4+8= 12

b)x=-19-5y
4(-19-5y)+y=0
-56-20y+y=0
-19y=56
y=-4
x=-19-5(-4)=-19+20=1

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