### Why won't sage math evaluate this expression?

**EDIT :** reformatted code

```
var('u_5 u beta')
```~~ ~~y = u - u_5 + beta*(exp(u)-u-4)
~~ ~~beta = 1.0
~~ ~~u_5 = -4.0
~~ ~~p = y.subs(u==u_5)
~~ p~~p

results in:

`0.0183156388887342*beta - u_5 - 4.00000000000000`

How can I get a numerical value? I did try numerical_approx, n() etc.

I expect it to multiply 0.0183... by 1 (beta) and subtract the -4 for u_5