Hi all,

I am using SymPy to try calculate this

\int_{A}^{B} ax+b \ dx

the function `f(x) = ax+b`

where `a`

and `b`

are constant in symbolics.

The integral is definite but, the interval of the integral is in symbolics too `A`

and `B`

.

I use this code, try them:

```
using SymPy
x, y, z = symbols("x y z")
A, B = symbols("A B")
integrate(ax+b, (x, A, B))
```

but it gets error:

**LoadError: UndefVarError: ax not defined**