1 | initial version |

Here I've displayed the X and Y axes as well as the axis of symmetry. I'm not sure what you are trying to do using "substitution".

```
f = lambda x,y:y^2-3*x-5*y+7
Yax = lambda x,y:x
Xax = lambda x,y:y
SYMAXIS = lambda x,y:y-5/2
p1=implicit_plot(f, (-4, 4), (-2, 6))
p2= point((1/4, 5/2), size = 45, color='red')
p3=implicit_plot(Yax, (-4, 4), (-2, 6),color='black')
p4=implicit_plot(Xax, (-4, 4), (-2, 6),color='black')
p5=implicit_plot(SYMAXIS, (-4, 4), (-2, 6),color='green')
p0=p1+p2+p3+p4+p5
show(p0)
```

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