Inverse Operations

The inverse of an operation is the operation which gets you back to the number you started with.

For example, if you start with the number 6 , and then add 4 :

6+4=10

To get back to the 6 , you have to subtract 4 from 10 .

104=6

Therefore addition and subtraction are inverse operations.

Similarly, division is the inverse of multiplication, and vice versa:

7×5=35 35÷5=7

The case of exponents and logarithms is slightly more complicated, since neither operation is commutative. After raising a number to a power, you can use the logarithm to get back to the exponent (not the base.)

10 3 =1000

log 3 100010 , but

log 10 1000=3