Equality constraints in optimization

Hi,

I have to minimize the volume of a heat transfer enhancement having geometrical parameters l1, l2 and h2

I have to furnish the following equality constraint in my optimization:

-26.143+4.3229(l2^2)+(l1^2)+4l1*l2=0 where both l1 and l2 are geometrical parameters and the value of l2 should change with that of l1 constrained by the above relation.

However, I do not know how to write this in COMSOL 5.2. Any suggestions would be appreciated.

Thanks, Mahvash