Let be tha statement that .

Where is any positive integer.

Check whether the statment is true for or not.

.

Therefore, is true for .

Assume that be true for .

.

Show that is also true.

The final statement is exactly .

Thus, is true.

Since is true for and implies that is also true.

Therefore, is true for .

By the mathematical induction principle, is true for all positive integers .

By the mathematical induction principle, is true for all positive integers .