Challenges

Remember the rules for this are

• Try to use only the information given up to this point in this book.
• Try not to give up until you've given it a solid attempt

Challenge 1

What will this program output when run? Write down your guess and then try running it.

void main() {
    double x = 5.1;
    double y = 2.4;
    System.out.println(x + y);
}

Challenge 2

What will this program output when run? Write down your guess and then try running it.

void main() {
    double x = 5.1;
    double y = 2.1;
    System.out.println(x + y);
}

Challenge 3

What will this program output when run? Write down your guess and then try running it.

How can you make it give the "right" answer?

void main() {
    double x = 5 / 2;
    System.out.println(x);
}

Challenge 4

These two expressions give different results. Why is that, and what results do they give?

void main() {
    double resultOne = (int) 5.0 / 2 + 5.0 / 2;
    double resultTwo = (int) (5.0 / 2 + 5.0 / 2);

    System.out.println(resultOne);
    System.out.println(resultTwo);
}

Challenge 5

The following is a quadratic equation.

\[ 2x^2 + 8x + 3 = 0 \]

To find the solutions of any quadratic equation you can use the following formula.

\[ x = \frac{-b \pm \sqrt{b^2 - 4ac} }{2a} \]

Where \(a\), \(b\), and \(c\) are the prefixes of each term in the following equation.

\[ ax^2 + bx + c = 0 \]

Write some code that finds both solutions to any quadratic equation defined by some variables a, b, and c. If the equation has imaginary solutions, you are allowed to just output NaN.

void main() {
    // For this one in particular, you should output
    // -3.5811388300842 and -0.41886116991581
    // but your code should work with these three numbers changed to
    // represent any given quadratic equation.
    double a = 2;
    double b = 8;
    double c = 3;

    double resultOne = ???;
    double resultTwo = ???;

    System.out.println(resultOne);
    System.out.println(resultTwo);
}