I could formulate you could formulate she could formulate we could formulate you could formulate they could formulate
V-ing form
I could be formulating you could be formulating she could be formulating we could be formulating you could be formulating they could be formulating
Perfect
I could have formulated you could have formulated she could have formulated we could have formulated you could have formulated they could have formulated
V-ing perfect
I could have been formulating you could have been formulating she could have been formulating we could have been formulating you could have been formulating they could have been formulating
Negation
Simple form
I couldn't formulate you couldn't formulate she couldn't formulate we couldn't formulate you couldn't formulate they couldn't formulate
V-ing form
I couldn't be formulating you couldn't be formulating she couldn't be formulating we couldn't be formulating you couldn't be formulating they couldn't be formulating
Perfect
I couldn't have formulated you couldn't have formulated she couldn't have formulated we couldn't have formulated you couldn't have formulated they couldn't have formulated
V-ing perfect
I couldn't have been formulating you couldn't have been formulating she couldn't have been formulating we couldn't have been formulating you couldn't have been formulating they couldn't have been formulating
Interrogative form
Simple form
could I formulate? could you formulate? could she formulate? could we formulate? could you formulate? could they formulate?
V-ing form
could I be formulating? could you be formulating? could she be formulating? could we be formulating? could you be formulating? could they be formulating?
Perfect
could I have formulated? could you have formulated? could she have formulated? could we have formulated? could you have formulated? could they have formulated?
V-ing perfect
could I have been formulating? could you have been formulating? could she have been formulating? could we have been formulating? could you have been formulating? could they have been formulating?
Interro-negative form
Simple form
couldn't I formulate? couldn't you formulate? couldn't she formulate? couldn't we formulate? couldn't you formulate? couldn't they formulate?
V-ing form
couldn't I be formulating? couldn't you be formulating? couldn't she be formulating? couldn't we be formulating? couldn't you be formulating? couldn't they be formulating?
Perfect
couldn't I have formulated? couldn't you have formulated? couldn't she have formulated? couldn't we have formulated? couldn't you have formulated? couldn't they have formulated?
V-ing perfect
couldn't I have been formulating? couldn't you have been formulating? couldn't she have been formulating? couldn't we have been formulating? couldn't you have been formulating? couldn't they have been formulating?