Answer :
7x+5y=-24 (1)
4x+y=42 (2)
multiply equation (2) by 5 to get
20x+5y=210 (3)
then calculate (3)-(2) which gives you
13x=234 hence x=18
then substitute for x in either equation to get y=-30
4x+y=42 (2)
multiply equation (2) by 5 to get
20x+5y=210 (3)
then calculate (3)-(2) which gives you
13x=234 hence x=18
then substitute for x in either equation to get y=-30
{ 7x + 5y = - 24
{ 4x + y = 42 ⇒ y = 42 - 4x
7x + 5y = - 24
7x + 5.( 42 - 4x ) = - 24
7x + 210 - 20x = - 24
7x - 20x = - 24 - 210
- 13x = - 234 .(-1)
13x = 234
x = 234
13
x = 18
4x + y = 42
4.(18) + y = 42
72 + y = 42
y = 42 - 72
y = - 30
S = { 18 , - 30 }
{ 4x + y = 42 ⇒ y = 42 - 4x
7x + 5y = - 24
7x + 5.( 42 - 4x ) = - 24
7x + 210 - 20x = - 24
7x - 20x = - 24 - 210
- 13x = - 234 .(-1)
13x = 234
x = 234
13
x = 18
4x + y = 42
4.(18) + y = 42
72 + y = 42
y = 42 - 72
y = - 30
S = { 18 , - 30 }
