Verbs with two different past tense forms
While many of the most common verbs in English are irregular (e.g. bring, forget), regular verbs far outnumber them. To form their past tenses regular verbs just add -ed or -d to their base form, e.g. talk => talked.
In particular, verbs that derive from nouns follow this regular pattern without exception. Indeed, this pattern is so firmly imprinted in our brains as a basic process for making nouns into verbs that if you were asked to make the invented noun flixxle into a verb you would automatically know how to.
However, there is a very small group of verbs whose past tenses can be either regular or irregular. They include:
They all contain an irregular verb as their second element: cast, put, and set.
Are their past tense and past participle therefore broadcast or broadcasted, forecast or forecasted, and so forth?
These alternative forms reflect two different analyses. If the verb is analysed as deriving from a noun, it is a regular verb, but it is an irregular verb when it is analysed as being based on the verb it contains.
In practice, although most dictionaries show both forms for all these verbs, people use the irregular form rather more often. The regular form is more frequently used in American English than elsewhere.
In these instances, you should use the past form that comes most naturally to you, while bearing in mind that other people may use a different one.