Question

Solve: x-3y=-9
4x+3y=-6

Answer 1

x - 3y = -9
-3y = -9 - x Multiply with -1

3y = 9 + x

4x + 3y= -6

4x + 9 + x = -6

5x + 9 = -6

5x = -6 - 9

5x = -15 Divide with 5

x= -15/5

x= -3

3y=9 + x

3y = 9 +(-3)

3y = 9 - 3

3y = 6 Divide with 3

y = 6/3

y= 2


Solution:

x = -3

y = 2

Answer 2

If we note that there is a +3y and a -3y in each of the equations, we simply add the two equations to get:
5x=-15, or x=-3
Substitute x=-3 in either one of the equations to get
-3-3y=-9
-3y=-6
y=2