Assuming that you are programming this...

unless |X| means absolute value which I am not sure it will be recognized on a computer.

Absolute value is extremely easy to do on a computer. All it requires is to switch the very first bit of a signed number and then subtract that from the highest possible signed value. Most languages support an abs() function, but it also works if you just do: x = (unsigned int) x or something similar.

But if you're on a computer, the above isn't needed.

if (X < 0) return -1; return 1;

x³ / ((x²)^9)^(1/6)

That will work but I don't know how you would do it in computer language.

Pretty easy actually:

(x*x*x) / pow((pow(x, 18)), 1/6)

If your language doesn't support a power function, you can write it yourself, although doing non integral powers is a bit tricky. But, as I said, you don't need to do all this.