Quadratic Calculator
Bugs

You are losing precision by calling sc.nextFloat() instead of sc.nextDouble().

If the equation has complex roots, Math.sqrt(discriminant) will crash.

Style

You are using too many variables to easily keep track of them mentally.  Also, it's better to avoid a giant block of declarations like your


double numOne, numTwo, numThree, negativeB,
        discriminant, divisor, sqRtDisc, dividendPlus,
        dividendMinus;



We know that we need to store at least a, b, and c, so let's start there.  Why not use the conventional terminology instead of numOne, numTwo, numThree?

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);

    System.out.println("Enter the value for A: ");
    double a = sc.nextDouble();

    System.out.println("Enter the value for B: ");
    double b = sc.nextDouble();

    System.out.println("Enter the value for C: ");
    double c = sc.nextDouble();


from there, the next important calculation is the discriminant, and optionally, its square root and the divisor.

    double discriminant = (b * b) - 4 * a * c;
    double divisor = 2 * a;


From there, you could go straight to formatting.  I suggest System.out.printf() for readability.

    if (discriminant &lt; 0) {         // Complex roots
        System.out.printf("x = %d + %d i\n",
                          -b / divisor, Math.sqrt(-discriminant) / divisor));
        System.out.printf("x = %d - %d i\n",
                          -b / divisor, Math.sqrt(-discriminant) / divisor));
    } else {
        System.out.println("x = " + (-b + Math.sqrt(discriminant)) / divisor);
        System.out.println("x = " + (-b - Math.sqrt(discriminant)) / divisor);
    }
}