[FIXED] How do I write a code for an f(x) equation to give its corresponding f(-x) in python?

Issue

I'm trying to write a function that accepts inputs of coefficients for polynomial f(x) and returns the corresponding f(-x). This is what I have so far:

import numpy as np
coeff = [1, -5, 2, -5]
poly = np.poly1d(coeff)
print (poly)

This prints out:

1x³ - 5x² + 2x - 5

I'm stuck here, since using poly(-x) or any values of x calculates the whole equation itself. Is there any workaround here? What I only want is for the code to do f(-x) such that 1(-1)³ - 5(-1)² + 2(-1) + 5 prints out:

-1x³ - 5x² - 2x - 5

Thank you!

Solution

The issue is that you are defining your polynomial by it's coefficients. I would instead define the variable x and let the module itself handle all the manipulations.

import numpy as np

x = np.poly1d([1,0])
p = x**3 - 5*x**2 + 2*x - 5
print(p(-x))

Answered By - Bobby Ocean