Respuesta :
Answer:
Step-by-step explanation:
(a) In order to use the elimination method, multiply the second equation by 2.
It becomes 2x + 4y = 20.
Subtract that from the first equation: 3x + 4y = 12
3x + 4y - 2x - 4y = 12 - 20
x = -8
Put that back in the second equation: -8 + 2y = 10
2y = 18
y = 9
(b) In order to use the substitution method, subtract 2y from the second equation.
It becomes x + 2y - 2y = 10 - 2y
x = 10 - 2y
Substitute that into the first equation:
3(10 - 2y) + 4y = 12
30 - 6y + 4y = 12
30 - 2y = 12
2y = 18
y = 9
Put back into the equation for x:
x = 10 - 2(9)
= 10 - 18
= -8
Answer:
Step-by-step explanation:
(1) 3x + 4y = 12
(2) x + 2y = 10
(2)*3: 3x+6y=30
by elimination (2)*3 - (1)
6y-4y=30-12
2y=18
y=9
x+2(9)=10
x=-8
rearrange (2): x=10-2y
substitute in (1): 3(10-2y)+4y=12
30-6y+4y=12
2y=30-12
y=9
x=10-2(9)
=-8
same ans either way