"I didn't spend" vs "I didn't spent" [closed]

Which is the correct grammar? Which is correct?


I didn't spend is correct. You must use the infinitive, not the simple past. (The helper verb do takes the simple past already.)


The negation of I spent is built by adding the basic form of the verb (in this case spend) to the negation of did.

I didn't spend.

Spent would be used in the present perfect.

I have spent $100.
I have not spent $900.