Question

change to negative -we did this exercise

Answer 1

hii,

this exercise is not undone by us

hope helps

Answer 2

heya,
we did this exercise- positive sentence.

'we didnt do this exercise' - negative sentence.

positive sentence- a sentence where we did it. we will never use 'not' in a positive sentence.
Negative sentence- a sentence which is not done. to make a negative sentence we have to use 'not'.

thank you.