1 | initial version |

When you do `solve(eqns,z)`

, Sage is trying to find z that satisfies both equations and finds that there is no such z. However, if you use `solve(eqns,[x,z])`

, it can find a solution and gives the one you want.

```
solve(eqns,[x,z])
```

gives

```
[[x == y, z == 2*y^2]]
```

For the simple elimination you suggest in your question, you could just do a substitution.

```
eq=x^2+y^2==z
eq.subs(x=y)
```

gives

```
z==2*y^2
```

Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.