I could formulate you could formulate he could formulate we could formulate you could formulate they could formulate
V-ing form
I could be formulating you could be formulating he could be formulating we could be formulating you could be formulating they could be formulating
Perfect
I could have formulated you could have formulated he 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 he 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 he 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 he 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 he 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 he 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 he formulate? could we formulate? could you formulate? could they formulate?
V-ing form
could I be formulating? could you be formulating? could he be formulating? could we be formulating? could you be formulating? could they be formulating?
Perfect
could I have formulated? could you have formulated? could he 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 he 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 he 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 he 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 he 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 he have been formulating? couldn't we have been formulating? couldn't you have been formulating? couldn't they have been formulating?