Add Lesson 1 Task 4

Lesson_1/task4.py

@@ -0,0 +1,32 @@
+# Lesson 1 Task 4: quadratic equation calculator
+# Author: Stanislav Mykhailenko
+# License: Unlicense
+
+# Return codes:
+# 0 - OK
+# 1 - Invalid numbers entered
+# 2 - Not a quadratic equation
+
+import sys, math
+
+try:
+	a = float(input("Enter number a: "))
+	b = float(input("Enter number b: "))
+	c = float(input("Enter number c: "))
+except ValueError:
+	print("Invalid numbers entered.")
+	sys.exit(1)
+
+if a == 0:
+	print("Not a quadratic equation.")
+	sys.exit(2)
+
+# Discriminant
+D = math.pow(b, 2) - 4 * a * c
+
+if D < 0:
+	print("No real roots exist.")
+elif D >= 0:
+	print("x₁ = " + str((-b + math.sqrt(D)) / (2 * a)))
+	if D > 0:
+		print("x₂ = " + str((-b - math.sqrt(D)) / (2 * a)))