Columns of tables in Desmos.com have different behavior depending their headings. If you put an function of x in the 2nd header we'll fill it in as a function table, calculating the values for you.
For example, if you have "x_1" and "2x_1+1" as your headings, we'll fill in the 2nd column for any point you put in the first:
Note that you can write rich math expressions in the cells, including things like pi/2:
To compare two functions side by side, add another column and enter another function into the new heading:
Note that you can convert any graphed function into a function table, by pressing the "edit" button, and then the "generate table" option for that function: