How to fix uneven object movement in Blender?

Question

Animation

In the 1st frame I set the X position to 1m, in the 20th frame - 20m.
But on the 2nd frame, the position along X is 1.15235m, and not the expected 2.
On the 3rd frame, the position is 1.58726m, not 3. In general, it moves unevenly.
How can this be fixed without manually correcting each frame?

Answer 1

RMB on Animation Panel > Interpolation Type > Linear