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Wednesday, 15 March 2017

Python Quadratic Formula


A equation with the form ax^2+bx+c=0 is known as a quadratic equation. When plotted on a graph it will take the general shape of the graph seen below. The points at which the quadratic graph crosses the x-axis are known as the solutions of the quadratic equation.















For this example the quadratic crosses the x-axis when x=3 and when x=-1.

The quadratic formula is used to find the values that satisfy the equation.
Quadratic Formula






I wrote a python script which can find the solutions of these quadratics by using the quadratic formula.

import math
print "ax^2+bx+c=0"

a = float(raw_input("Please enter the value of a: "))
b = float(raw_input("Please enter the value of b: "))
c = float(raw_input("Please enter the value of c: "))

try:
  x1 = (-b + math.pow((math.pow(b,2)-(4*a*c)),0.5)) / 2*a
  x2 = (-b - math.pow((math.pow(b,2)-(4*a*c)),0.5)) / 2*a
except ValueError:
  print "No real solutions"
  exit()

print  "X solutions: ", x1, ",",x2

The Quadratic formula has been wrapped in a try statement to prevent the program from crashing if a quadratic equation with no real solutions is entered. This would cause a crash as you would be trying to find the square root of a negative number which is not possible.

Wednesday, 22 February 2017

Check root at start of script

Some scripts need to be run as root and you may want to check at the start of that script that it is running as root. This can be done by checking the environment variable $EUID. This variable will hold the value 0 if it's being run as root.


#!/bin/bash
if [ "$EUID" -ne 0 ];then
echo "Please run this script as root"
exit 1
fi