# Mathetica function (help fix my equation please)

1. Mar 15, 2016

### Shawj02

Hi guys,

I have a problem with Mathematica. The equation (see attachment) is SUPPOSE TO give:
n[0]=n0
n[1]=x0-n0
n[2]=x1-x0+n0
n[3]=x2-x1+x0-n0
n[4]=x3-x2+x1-x0+n0
n[5]=x4-x3+x2-x1+x0-n0
n[6]=x5-x4+x3-x2+x1-x0+n0-1
...

But when I put in n[1] I get the following errors and output:

Sum::itraw: Raw object 1 cannot be used as an iterator. >>
Sum::vloc: The variable 1 cannot be localized so that it can be assigned to numerical values. >>
Sum::itraw: Raw object 1 cannot be used as an iterator. >>
Sum::vloc: The variable 1 cannot be localized so that it can be assigned to numerical values. >>
$$\sum _{1=1}^1 (-1)^{1-1} x_{1-1}-n_0$$

What do I need to change to give me an output of $$x_ 0 + n_ 0$$

n[2] gives:
$$\sum _{2=1}^2 (-1)^2 x_{2-1}+n_0$$
when I want it to give me: $$x_1-x_0-n_0$$

#### Attached Files:

• ###### 1.jpg
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Last edited: Mar 15, 2016
2. Mar 15, 2016

### Staff: Mentor

3. Mar 15, 2016

### Shawj02

I been playing around with the LATEX thing.. using Mathematica's right click and "copy as Latex" function.
I have attached a copy of my original equation, below is an attempt to convert it into Latex.

$$\sum _{z=1}^z (-1)^z x_{z-1}-\sum _{z=6}^z 1+n_0 (-1)^z$$

There seems to be a problem with "Reals" and "Absolutes" How do I do these in Latex?

#### Attached Files:

• ###### 1.jpg
File size:
7.6 KB
Views:
54
Last edited: Mar 15, 2016
4. Mar 15, 2016

### Staff: Mentor

The problem is your summation.
$$\sum _{z=1}^z f(z)$$ is bad input. It should be something like
$$\sum _{i=1}^z f(i)$$

5. Mar 15, 2016

### Shawj02

Yep, you're right! I've got it working perfectly now!

My other question is: How do I write the ABS and REALS in LATEX? (so I can post things on physics forms better)

so far i've got:

$$\sum _{j=1}^z (-1)^j x_{j-1}-\sum _{j=6}^z 1+n_0 (-1)^z$$

#### Attached Files:

• ###### 2.jpg
File size:
7.4 KB
Views:
51
6. Mar 15, 2016

### Staff: Mentor

When I am trying to troubleshoot I would rather just have the straight code. The fancy formatting is nice, but makes finding code errors more difficult. I know that isn't everyone's preference, but it is my preference. I would just use the "code" tag and copy and paste the Mathematica input.