Constants, as the name implies, remain constant, which means that their value never changes.
For example, 2 is always 2 and 9.4 is always 9.4, and variable values, on the other hand, can vary. Considering the variable 2x as an example.
When [tex]x = 1, 2x =2[/tex] and when [tex]x = 2, 2x = 4[/tex], hence the value of [tex]2x[/tex] varies depending on what [tex]x[/tex] is.
We can't combine constants and variables and they're not the same item; one can change while another can't, and you can't join terms that are not the same.
