import math

def repeater(s1, s2, n):
	'''
	(str, str, int) -> str
	Returns a silly string: i.e. s1 and s2 concatinated
	and repeated n times and deliminated by underscore
	'''
     
	s = s1+s2
	return "_" + (s*n) + "_"


def reverse(x):
	'''
	(int) -> int
	Returns integer x with reversed digits

	Precondition: x is a two digit positive integer
	'''
     
	high_digit = x // 10
	low_digit = x % 10
	return low_digit * 10 + high_digit


def roots(a, b, c):
	'''
	(number, number, number) -> None
	Prints nicely the soluitons of the quadratic equation
	with ccoefficients a, b, c

	Preconditions:
		a is not equal to zero and
	   b*b-4ac is not a negative number '''
	
	x1 = (-b+math.sqrt(b**2 - 4*a*c))/2*a
	x2 = (-b-math.sqrt(b**2 - 4*a*c))/2*a

	print ("The quadratic equation with coefficients a =", a, "b =", b, "c =", c)
	print ("has the following solutions (i.e. roots): ")
	print (x1, " and", x2)

	
def real_roots(a, b, c):
	'''
	(number, number, number) -> boolean

	Returns True if the quadratic equation with
	coefficients a, b, c has real roots. False otherwise
	'''

     return b**2 - 4*a*c >= 0