As per Lagrange theorem it says I can get maximum or minimum under some constraint.
Example:
$f(x,y)=x^2+y^2+4$ under constraint $x+y=2$. I can use Lagrange theorem for this.
But I have a problem like $f(x,y)=x^2+y^2+4$ under constraint like $x$ should be minimum.
How can I solve this any theorem or solution?