Question

Solve, using linear combination. 11x + 4y = 18 3x + 4y = 2

Answer 1

11x + 4y = 18
3x + 4y = 2.....multiply by -1
----------------
11x + 4y = 18
-3x - 4y = -2 (result of multiplying by -1)
---------------add
8x = 16
x = 16/8
x = 2

3x + 4y = 2
3(2) + 4y = 2
6 + 4y = 2
4y = 2 - 6
4y = -4
y = -4/4
y = -1

solution is : (2,-1)

Answer 2

11 x + 4 y = 18
3 x + 4 y = 2 

11 x + 4 y = 18 
- 3 x - 4 y = - 2 

8 x = 16 
x = 2 

11 x + 4 y = 18
22 + 4 y = 18
4 y = 18 - 22 
4 y = - 4 
y = - 1 

S ( - 1 ; 2)