You can see that you add 1x to each expression in the sequence, which means that the first expression will be 2x, and the second one 3x. You also add 2 to each x, which means that the first expression will be 1, and the second one 2.
2x+1, 3x+3, 4x+5, 5x+7, 6x+9, 7x+11, 8x+13....
