Question

1- Qual a solução dos sistemas a seguir?

a+2b = 2 a+b : 2 = 2
3a+b=20 a-b : 4 = 4

Answer 1

1°
{a+2b=2
{(a+b)÷2=2

a=2-2b

(a+b)÷2=2
(2-2b+b)÷2=2
(2-b)÷2=2
2-b=2×2
2-b=4
-b=4÷2
-b=2
b=-2

a=2-2b
a=2-2×(-2)
a=2+4
a=6

a=6, b=-2


2°
{3a+b=20
{(a-b)÷4=4

b=20-3a

(a-20-3a)÷4=4
(-2a-20)÷4=4
-2a-20=4×4
-2a-20=16
-2a=16+20
-2a=36
a=36÷(-2)
a=-18

b=20-3a
b=20-3×(-18)
b=20+54
b=74

a=-18, b=74