1)Elimination by coefficient method
3x - 9y = 3 .....( i )
6x - 3y = - 24 ...( ii )
Multiplying ( i ) by 2,we get
6x - 18y = 6 .... ( iii )
Subtracting ( ii ) from ( iii ),we get
6x - 18y = 6
6x - 3y = - 24
(-) (+) (+)
---------------------
- 15y = 30
y = - 2
Substituting y = - 2 in ( ii ),we get
6x - 3(- 2) = - 24
6x + 6 = - 24
6x = - 30
x = - 5
x = - 5 and y = - 2 is the solution of given simultaneous equations.
2)Substitution method
3x - 9y = 3
Dividing throughout by 3,we get
x - 3y = 1
x = 1 + 3y ..... ( i )
6x - 3y = - 24 .....( ii )
Substituting ( i ) in ( ii ),we get
6(1 + 3y) - 3y = - 24
6 + 18y - 3y = - 24
15y = - 30
y = - 2
Substituting y = - 2 in ( i ),we get
x = 1 + 3y
x = 1 + 3(- 2)
x = 1 - 6
x = - 5
x = - 5 and y = - 2 is the solution of given simultaneous equations.
According to me both the methods are efficient and easy.
It varies from individual to individual to decide which method is efficient.
So my opinion to you is that learn both the methods and practice hard and try to master them.
!!!HOPE I HELPED!!!!