I need to define

```
$y1(k)=\frac{y_{k+1}-y_{k-1}}{2*h}$
```

in sage so that sage can differ between symbolic $$y_{k+1}$$ and $$y_{k}$$.

Would somebody please help?

1 | initial version |

I need to define

```
$y1(k)=\frac{y_{k+1}-y_{k-1}}{2*h}$
```

in sage so that sage can differ between symbolic $$y_{k+1}$$ and $$y_{k}$$.

Would somebody please help?

2 | No.2 Revision |

I need to ~~define~~define $$y1(k)=\frac{y_{k+1}-y_{k-1}}{2*h}$$

```
$y1(k)=\frac{y_{k+1}-y_{k-1}}{2*h}$
```

in sage so that sage can differ between symbolic $$y_{k+1}$$ and $$y_{k}$$.

Would somebody please help?

3 | retagged |

I need to define $$y1(k)=\frac{y_{k+1}-y_{k-1}}{2*h}$$

in sage so that sage can differ between symbolic $$y_{k+1}$$ and $$y_{k}$$.

Would somebody please help?

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