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Python | sympy.ff() method
  • Last Updated : 14 Jul, 2019

With the help of sympy.ff() method, we can find the Falling factorial. Falling factorial is defined by –

 ff(x, k) = x \cdot (x-1) \cdots (x-k+1)

where x can be arbitrary expression and k is an integer.

Syntax: ff(x, k)

Parameter:
x – It denotes any arbitrary expression.
k – It denotes an integer.

Returns: Returns falling factorial corresponding to the given inputs.



Example #1:




# import sympy 
from sympy import * 
  
x = symbols('x')
k = 5
print("Value of x = {} and k = {}".format(x, k))
   
# Use sympy.ff() method 
ff_x_k = ff(x, k)  
      
print("Falling factorial ff(x, k) : {}".format(ff_x_k))  

Output:

Value of x = x and k = 5
Falling factorial ff(x, k) : x*(x - 4)*(x - 3)*(x - 2)*(x - 1)

Example #2:




# import sympy 
from sympy import * x = 7
k = 5
print("Value of x = {} and k = {}".format(x, k))
   
# Use sympy.ff() method 
ff_x_k = ff(x, k)  
      
print("Falling factorial ff(x, k) : {}".format(ff_x_k))  

Output:

Value of x = 7 and k = 5
Falling factorial ff(x, k) : 2520

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