Simultaneous Equations


   
 
Substitution Method
 
Solve 2x - 9y = 0 …(i)
 
x - 18y = 27 … (ii)
 
 
From (i)
 
2x - 9y = 0
 
2x = 9y
 
…(iii)
 
Substituting this value of x in (ii), we get,
 
 
9y - 36y = 54
 
- 27y = 54 y = -2
 
Substitute this value of y in (iii):
 
 
= - 9
 
The solution is x = -9 and y = -2.
 
 
Solve 43x + 31y = 241 …(i)
 
31x + 43y = 277 …(ii)
 
 
By adding (i) and (ii), we get
 
74x + 74y = 518
 
x + y = 7 …(iii)
 
By subtracting (ii) from (i)
 
12x - 12y = -36
 
or x - y = -3 …(iv)
 
By adding (iii) and (iv) 2x = 4 x = 2
 
Substituting x = 2 in (iii), we get:
 
(2) + y = 7 y = 5
 
The solution is x = 2 and y = 5.
 
 
Solve: …(i)
 
…(ii)
 
 
Let and
 
(i) and (ii) can be written as
 
5a - 2b = 2 …(iii)
 
2a + 3b = 16 …(iv)
 
Multiplying (iii) by 3 and (iv) by 2, we get
 
15a - 6b = 6 …(v)
 
4a + 6b = 32 …(vi)
 
Adding (v) and (vi), we get 19a = 38 a = 2
 
Substituting a = 2 in (iv), we get
 
2(2) + 3b = 16
 
3b = 12 b = 4
 
Re-substituting
 
 
 
The solution is
 
 
     
   
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