3a+b=10, 2a+4b=0

Answer 1

3 a + b = 10
-
2 a + 4 b = 0
__________
3 a - 2 a + b - 4 b = 10 - 0

a - 3 b = 10

Add 3 b to both sides

a = 10 + 3 b

Substitute this value in one of equations ( never mind wich ). In this case in first equation.

3 a + b = 10

3 ( 10 + 3 b ) + b = 10

3 ∙ 10 + 3 ∙ 3 b + b = 10

30 + 9 b + b = 10

30 + 10 b = 10

Subtract 30 to both side

10 b = - 20

Divide both sides by 10

b = - 2

a = 10 + 3 b

a = 10 + 3 ∙ ( - 2 )

a = 10 - 6

a = 4

Solution:

a = 4 , b = - 2

Proof:

3 a + b = 10

3 ∙ 4 + ( - 2 ) = 10

12 - 2 = 10

10 = 10

2 a + 4 b = 0

2 ∙ 4 + 4 ∙ ( - 2 ) = 0

8 - 8 = 0

0 = 0

Answer 2

Use substitution,
from the first: b = 10-3a
into the second
2a+4b=0
2a + 4(10-3a) = 0
2a + 40 - 12a = 0
-10a = -40
a = 4
then b = 10-4b = 10-16 = -6

Answer 3

Mathematics

Answer 4

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Answer 5

A=4,b=-2