This problem is 'simple' ( i am told) Its from chapter 7 (Optimization of Functionals) of Luenbergers book "Optimization by vector space methods" but...

This problem is 'simple' ( i am told)Its from chapter 7 (Optimization of Functionals) of Luenbergers book "Optimization by vector space methods" but i think it can be solved using basic math. If any of you have taken proof-based math please check it out and see if you can help. And If you guys would like me to upload the chapter I can.