PDA

View Full Version : Find the values of w and z in simultaneous eqn?



momoko
06-06-2009, 09:17 PM
Find the values of w and z if (2w + 4, z - 3w) is the solution of the simultaneous equations x/3 + 4y = 33 and 3x - y/3 = -30.


I have no idea how to solve this problem, but this is the work I've done so far anyway:
x/3 + 4y = 33 ----- (1)
3x - y/3 = 30 ----- (2)
Substitute (2w + 4, z - 3w) into (1) and (2),
(2w + 4)/3 + 4(z - 3w) = 33
(2w + 4)/3 + 4z - 12w) = 33 ----(3)
3(2w + 4) - (z - 3w)/3 = -30
6w + 12 - (z - 3w)/3 = -30
6w - (z - 3w)/3 = -42 ---- (4)

i don't really understand what to do now. any help would be really greatly appreciated :D

Denis
06-06-2009, 11:36 PM
(2w + 4)/3 + 4z - 12w = 33 ----(3)
6w - (z - 3w)/3 = -42 ---- (4)

Multiply each by 3:

2w + 4 + 12z - 36w = 99 ----(3)

18w - z + 3w = -126 ---- (4)

I'll let you finish it.