I could backsolve you could backsolve he could backsolve we could backsolve you could backsolve they could backsolve
V-ing form
I could be backsolving you could be backsolving he could be backsolving we could be backsolving you could be backsolving they could be backsolving
Perfect
I could have backsolved you could have backsolved he could have backsolved we could have backsolved you could have backsolved they could have backsolved
V-ing perfect
I could have been backsolving you could have been backsolving he could have been backsolving we could have been backsolving you could have been backsolving they could have been backsolving
Negation
Simple form
I couldn't backsolve you couldn't backsolve he couldn't backsolve we couldn't backsolve you couldn't backsolve they couldn't backsolve
V-ing form
I couldn't be backsolving you couldn't be backsolving he couldn't be backsolving we couldn't be backsolving you couldn't be backsolving they couldn't be backsolving
Perfect
I couldn't have backsolved you couldn't have backsolved he couldn't have backsolved we couldn't have backsolved you couldn't have backsolved they couldn't have backsolved
V-ing perfect
I couldn't have been backsolving you couldn't have been backsolving he couldn't have been backsolving we couldn't have been backsolving you couldn't have been backsolving they couldn't have been backsolving
Interrogative form
Simple form
could I backsolve? could you backsolve? could he backsolve? could we backsolve? could you backsolve? could they backsolve?
V-ing form
could I be backsolving? could you be backsolving? could he be backsolving? could we be backsolving? could you be backsolving? could they be backsolving?
Perfect
could I have backsolved? could you have backsolved? could he have backsolved? could we have backsolved? could you have backsolved? could they have backsolved?
V-ing perfect
could I have been backsolving? could you have been backsolving? could he have been backsolving? could we have been backsolving? could you have been backsolving? could they have been backsolving?
Interro-negative form
Simple form
couldn't I backsolve? couldn't you backsolve? couldn't he backsolve? couldn't we backsolve? couldn't you backsolve? couldn't they backsolve?
V-ing form
couldn't I be backsolving? couldn't you be backsolving? couldn't he be backsolving? couldn't we be backsolving? couldn't you be backsolving? couldn't they be backsolving?
Perfect
couldn't I have backsolved? couldn't you have backsolved? couldn't he have backsolved? couldn't we have backsolved? couldn't you have backsolved? couldn't they have backsolved?
V-ing perfect
couldn't I have been backsolving? couldn't you have been backsolving? couldn't he have been backsolving? couldn't we have been backsolving? couldn't you have been backsolving? couldn't they have been backsolving?