Under the Constitution, government is allowed to discriminate in some way among groups of people. Otherwise, the government would be unable to provide for different people with different needs.
Discriminate in this case can be understood as differentiate, rather than discriminate. Without this discrimination, the government wouldn't be able to understand and address the different needs of different people, depending on their health status, physical and economical condition, etc.
Potassium-argon dating, method of determining the time of origin of rocks by measuring the ratio of radioactive argon to radioactive potassium in the rock. This dating method is based upon the decay of radioactive potassium-40 to radioactive argon-40 in minerals and rocks; potassium-40 also decays to calcium-40.