Im studing complexity theory and im reading this question on Quora.
According to what the guy is saying : if we are able to solve a NP-Hard problem in polynomial time we have prooved that P=NP. But, in P we find problems that can be solved and checked in polynomial time and in this case we have only prooved that NP problems can be solved in polynomial time, but we dont know if this implies that can be also checked in polynomial time.