EXCEL subtraction operation doubt! ! ! !

A whole set of a less rigid cell, such as B2 = A2-A1, B3 = A3-A1, B4 = A4-A1 how to enter operation ah, the younger brother B2, B3, B4 after the pull-down operation, B5 should not be allowed to have found the same A5-A1, and they would even be able to do what the drop-down operations are the results of the implementation of the operation minus A1 ah??

with no reference to A1 into $ A $ 1 under test to add $ A1, to lock in to make it into a “$ A $ 1 “,”$” the keyboard symbols in the top 4 in English Enter a state of holding down the shift, and then 4 on the line, = A2-$ A $ 1 in the B2 enter = A2-$ A $ 1, you can enter.Select B2, then the cursor will be held on the lower right corner point, drag and drop Other filled to complete computing.Upstairs correct, add:
publicity cell activation (F2 key or double-click) later in the F4 key A1, $ A $ 1, A $ 1, $ A1 in switching back and forth, they represent Different quote.