Theory: Chapter 4, Logic (p. 21-27)
Exercises: Chapter 4 (reading)
Homework: Write a program that solves the quadratic equation ax2+bx+c = 0.
It accepts the three coefficients a, b, c and prints one of the following:
the x1, x2 roots of the equation
the message "no roots"
the message "equation impossible"
the message "equation indefinite"