Help with a simple equation

regulus · 11 Apr 2012 at 20:09

Ok, I almost feel embarrassed to ask as I should know this but here go.

7x + 3 = 5x - 4

I conclude x = positive 7 over 2

Wolfram says negative 7 over 2.

Can anyone just write down step by step to tell me where I'm going wrong.

Yes I know, school stuff. It's been a few years for me since

Before you ask, I'm trying to write software (for fun) which calculate variables and solve simple algebraic equations. It's strange that the equations stump me whilst the software don't

quickshot89 · 11 Apr 2012 at 20:11

7x + 3 = 5x - 4

7x + 7 = 5x

2x + 7 = 0

2x = -7

x = -7/2

Destination · 11 Apr 2012 at 20:13

7x - 5x = -4 -3
2x = -7
X= -7/2

regulus · 11 Apr 2012 at 20:15

2x = -7 .... I got stumped there

I had it as;

2x + 7 = 0 and I divided 2/2 and 7/2 on the left side of the 'equal to' which were both positive.

regulus · 11 Apr 2012 at 20:16

Hikari Kisugi said:
7x - 5x = -4 -3
2x = -7
X= -7/2

That's a good explanation. Quicker than the way I did it.

Ok, thanks all.

touch · 11 Apr 2012 at 20:20

regulus said:
I had it as;

2x + 7 = 0 and I divided 2/2 and 7/2 on the left side of the 'equal to' which were both positive.

That is a correct way to do it, you just havnt quite finished it.

2x + 7 = 0
2x/2 + 7/2 = 0/2
2/2x = -7/2
x = -7/2