I have built this function which calls a couple other functions to get the oprator and numbers for an arithmetic operation but I get the error `function call: expected a function after the open parenthesis, but received '+`

. normaly you invoke addition as (+ 5 6) and multiplication as (* 4 9) ect. So I thought you could call a function that would get each piece but I cant seem to get it to work. Here is what I have:

```
(define calculate
(lambda (x)
((getOperator x) (getOperand1 x) (getOperand2 x))
)
)
```

Detailed explanations as to the reasons why what I'm doing is wrong are greatly apreciated.

Thanks