Then f of 3, 3 minus 1 is 2, square root of 2. So the function evaluated at 3 is the square root of 2, so this is going to be 2 times the square root of 2. Then the function evaluated at 4. When you evaluate at 4, you get the square root of 3, so this is going to be 2 times the square root of 3. Then you get 2 times the square root of 4. 5 minus 1 is 4. 2 times the square root of 4 is just 4.