# Operations on Reductive Groups

## `GetSplitPrimeWithSquare(G): GrpRed -> RngIntElt`

```magma
LowerBound: RngIntElt                    Default: 2
```

Given a reductive group $G$ over ${\mathbb{Q}}$, returns a prime $p$ where $G_p$ is split, and $2$ is a square.

## Base change

### `ChangeRing(G, S): GrpRed, Rng -> GrpRed`

Given a reductive group $G$ with base ring $R$, together with a ring $S$, construct the reductive group $G_S$ with base ring $S$ obtained by coercing the coefficients of elements of $R$ into $S$.