public class Ch02Homework {

    //Use the main subroutine to check your other subroutines.
    //The main subroutine is not graded at all. It can remain blank.
    public static void main(String[] args) {

    }

    /**
     * This function returns the slope of the line through the points
     * (x1, y1) and (x2, y2).
     * Precondition: The line must have a defined slope.
     * @param x1 the x coordinate of the first point
     * @param y1 the y coordinate of the first point
     * @param x2 the x coordinate of the second point
     * @param y2 the y coordinate of the second point
     * @return the slope of the line
     */
    public static double slope(double x1, double y1, double x2, double y2) {
        return ((y1 - y2) / (x1 - x2));
    }

    /**
     * This function returns the geometric mean of number1 and number2
     * Precondition: number1 and number2 must both be positive
     * @param number1 any positive number
     * @param number2 any positive number
     * @return the geometric mean of the numbers
     */
    public static double geometricMean(double number1, double number2) {
        return Math.sqrt(number1 * number2);
    }

    /**
     * This function returns the larger of the two solutions to the
     * quadratic equation a*x^2 + b*x + c = 0.
     * Precondition: A solution must exist.
     * @param a the coefficient of the squared term
     * @param b the coefficient of the linear term
     * @param c the constant term
     * @return the larger of the two solutions to the equation
     */
    public static double quadraticSolution(double a, double b, double c) {
        if ((-b + Math.sqrt((b * b) - 4 * a * c))/2 * a) > ((-b - Math.sqrt((b * b) - 4 * a * c))/2 * a){
            return ((-b + Math.sqrt((b * b) - 4 * a * c))/2 * a);
        }

        else {
            return ((-b + Math.sqrt((b * b) - 4 * a * c))/2 * a);
        }
    }

    /**
     * This function returns a String consisting of the first and last letters
     * of the parameter str.
     * Example: firstAndLast("hello") --> "ho"
     * Example: firstAndLast("x") --> "xx"
     * Precondition: the parameter str must be a String of alpha-characters
     * @param str any non-empty String
     * @return the first and last letters of the parameter str
     */
    public static String firstAndLast(String str) {
        if (str.length() == 1){
            return str + str;
        }

        else if (str.length() == 2){
            return str;
        }

        else{
            return str.substring(0,0) + charAt(str.length()-1, str.length()); ;
        }
    }

    /**
     * This function returns a modified version of the parameter str
     * with the first and last letters lowercase and all the
     * remaining letters capitalized.
     * Example: middleCapitalization("HelLo") --> "hELLo"
     * Example: middleCapitalization("X") --> "x"
     * Example: middleCapitalization("oK") --> "ok"
     * Example: middleCapitalization("") --> ""
     * @param str any String
     * @return a modified version of the parameter str
     */
    public static String middleCapitalization(String str) {
        return "Hello";
    }

}