# interact variable not found

I keep getting ValueError: Variable 'h' not found when I try to plot an interact:

```
f = (x-h)^2 - 4*a*(y-k)
Parabola = solve(f,y)[0].rhs()
print(Parabola)
@interact
def _(h=slider(-5,5,default=1), a=slider(-5,5,default=1), k=slider(-5,5,default=1)):
show(plot(Parabola,x,-5,5))
```

It even creates the sliders but the plot can't see h. What am I doing wrong? print(Parabola)