Question

Resolva os sistemas:
1) 3x-y=18
x+y= 10

2)x+5/5=x-y/3
x/2=y+2

3) x=2(y+2)
x-y/10=x/2+2

Answer 1

1)
3x-y=18
x+y=10  ====>> x=10-y

3(10-y)-y=18
30-3y-y=18
-4y=-12
y=12/4
y=3

x=10-y
x=10-3
x=7
Resposta: x=7 e y=3

2)
x+5/5 = x-y/3
x/2 = y+2  =====>> x = 2y+4

2y+4+5/5 = 2y+4-y/3 (multiplica cruzado)
6y+12+15 = 10y+20-5y
6y+27 = 5y+20
6y-5y = 20-27
y= -7

x= 2y+4
x= 2(-7)+4
x= -10
Resposta: x= -10 e y= -7

3)
x=2(y+2)  ======>> x = 2y+4
x-y/10=x/2+2

2y+4-y/10 = 2y+4/2+2
y+4/10 = 2y+4/4 (multiplica cruzado)
4y+16 = 20y+40
20y-4y= 16-40
16y = -24
y = -24/16
y = -3/2

x = 2(-3/2)+4
x = (-6/2)+4
x = -3+4
x = 1
Resposta: x= 1 e y= -3/2