**Solution:**

To find the value of x^3 - 3x, we first need to simplify the expression Ifx.

**Simplifying Ifx:**

Ifx = (4√15)^(1/3) * (4 - √15)^(3/3) * 5

Let's simplify each term separately:

1. Simplifying (4√15)^(1/3):
- We can rewrite 4√15 as 4 * (√15).
- Now, (4 * (√15))^(1/3) can be written as (4^(1/3)) * (√15)^(1/3).
- √15 can be written as 15^(1/2), so we have (4^(1/3)) * (15^(1/2))^(1/3).
- By applying the exponent rule, we get (4^(1/3)) * (15^(1/6)).
- Since 4 = 2^2, we can simplify further as (2^2)^(1/3) * (15^(1/6)).
- Applying the exponent rule again, we have 2^(2/3) * 15^(1/6).
- Finally, we can rewrite 2^(2/3) as (2^(1/3))^2, so we have (2^(1/3))^2 * 15^(1/6).
- The cube root of 2 is ∛2, so the simplified term becomes (∛2)^2 * 15^(1/6).

2. Simplifying (4 - √15)^(3/3):
- The term (4 - √15) can be left as it is because the exponent 3/3 cancels out.
- Therefore, (4 - √15)^(3/3) simplifies to (4 - √15).

Now, let's substitute the simplified terms back into the original expression:

Ifx = (∛2)^2 * 15^(1/6) * (4 - √15) * 5

**Simplifying the expression x^3 - 3x:**

From the given expression, we can see that x^3 - 3x is in the form of a difference of cubes, which can be factored using the formula: a^3 - b^3 = (a - b)(a^2 + ab + b^2).

In our case, a = x and b = ∛2. So, we can rewrite x^3 - 3x as:
x^3 - 3x = (∛2)^3 - 3(∛2)

Let's simplify each term:

1. Simplifying (∛2)^3:
- (∛2)^3 can be written as 2^(3/2).
- Since 2^(3/2) = √(2^3), we have √8.
- Therefore, (∛2)^3 simplifies to √8.

2. Simplifying 3(∛2):
- Since 3(∛2) cannot be simplified further, it remains the same.

Now, substituting the simplified terms back into the expression, we have:

x^3 - 3