I wouldn't use `<br/>`, it makes things look cramped. In fact, I'd split this into two separate hints, and I'd have an additional step.

Something like (using an example I saw):

1) The formula 

2) `f(5)=950, f(2)=68`

3) (f(5) − f(2)) / (5−2) = (950 - 68) / 3

4) = 294