# Simultaneous Equations

• Jul 12th 2008, 01:48 PM
princess_anna57
Simultaneous Equations
Solve:

2x + 4 = 4
3x - y = 1

Solve:
x - 2y = 7
2x + y = 4

Please give step by step instructions. Thank you.
• Jul 12th 2008, 02:22 PM
janvdl
Quote:

Originally Posted by princess_anna57
Solve:

2x + 4 = 4
3x - y = 1

Please double check that you did not make a typo here.

2x + 4 = 4
2x = 4 - 4
2x = 0
x = 0

We now know x = 0

3x - y = 1
3(0) - y = 1
y = -1

Thus:
x = 0
y = -1

Solve:
x - 2y = 7
2x + y = 4

x - 2y = 7
x = 7 + 2y (Set this value for x into the second equation)

2(7 + 2y) + y = 4
14 + 4y + y = 4
5y = -10
y = -2

Now we have a value for y. (y = -2)
Set this value into the first equation.

x -2(-2) = 7
x + 4 = 7
x = 3

Please give step by step instructions. Thank you.

Responses in red. (Happy)
• Jul 12th 2008, 02:40 PM
princess_anna57
Thank you
Nope, no typos in the equations. Thanks a lot.
• Jul 12th 2008, 02:42 PM
janvdl
Quote:

Originally Posted by princess_anna57
Nope, no typos in the equations. Thanks a lot.

You are welcome :)