Problem 16 - Applied Mathematics: For the Managerial, Life, and Social Sciences

Question

In Exercises, factor the polynomial. If the polynomial is prime, state it. $$ m^{2}+2 m+3 $$

Step-by-Step Solution

Answer

The given polynomial, \(m^2 + 2m + 3\), is prime since its discriminant is negative (\(D = -8\)).

Step 1: Determine If the Polynomial Can Be Factored

First, we need to check if the given quadratic polynomial can be factored. For a quadratic polynomial of the form \(ax^2 + bx + c\), we can use the discriminant to determine if it can be factored. The discriminant is given by the formula: \[D = b^2 - 4ac\] Here, \(a = 1\), \(b = 2\), and \(c = 3\).

Step 2: Calculate the Discriminant

Now let's calculate the discriminant using the values of \(a\), \(b\), and \(c\): \[D = (2)^2 - 4(1)(3)\] \[D = 4 - 12\] \[D = -8\]

Step 3: Determine If the Polynomial Is Prime or Factorable

Since the discriminant is negative (\(D = -8\)), the given quadratic polynomial cannot be factored using real numbers. In this case, we would say that the polynomial is prime. So, the given polynomial, \(m^2 + 2m + 3\), is prime.

Key Concepts

Quadratic Polynomials

Quadratic polynomials are algebraic expressions of the form \(ax^2 + bx + c\), where \(a\), \(b\), and \(c\) are constants and \(a \eq 0\). They are called quadratic because the highest degree of the variable \(x\) is 2, which is referred to as a second-degree polynomial.

These polynomials graph into a parabola when plotted on a coordinate axis, and this curve can open either upwards or downwards depending on the sign of the coefficient \(a\). When \(a > 0\), the parabola opens upwards, and when \(a < 0\), it opens downwards.

Factoring quadratic polynomials involves finding two binomials that, when multiplied together, give you the original quadratic polynomial. The most common method to factor these polynomials is to find two numbers that add up to \(b\) and multiply to \(ac\). However, sometimes it's not possible to factor them this way, especially if the polynomial is prime, which we will discuss in the following sections.

Discriminant in Quadratics

The discriminant in the context of quadratic polynomials is a very useful concept, especially when it comes to factoring. The discriminant is the part of the quadratic formula \(\frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\) under the square root sign and is denoted by \(D\). The formula for the discriminant is \(D = b^2 - 4ac\).

The value of the discriminant can tell us about the nature of the roots of a quadratic equation:

• If \(D > 0\), there are two distinct real roots.
• If \(D = 0\), there is exactly one real root (also called a repeated root).
• If \(D < 0\), there are no real roots, but there are two complex roots.

When factoring a quadratic polynomial, a negative discriminant means the polynomial cannot be factored into real number factors, and it is thus considered to be a prime polynomial.

Prime Polynomials

Prime polynomials, also known as irreducible polynomials, are polynomials that cannot be factored into the product of two non-constant polynomials. In simpler terms, if no real numbers can multiply together to give the polynomial, then it is prime.

In the context of quadratic polynomials, a prime polynomial occurs when the discriminant is less than zero. This indicates that there are no real solutions to the equation \(ax^2 + bx + c = 0\) and as such, no real factors that can be multiplied to get the polynomial. In the example given, the polynomial \(m^2 + 2m + 3\) is prime because its discriminant \(D = -8\) is less than zero, signifying that it has complex roots and can not be factored over the real numbers.

Understanding when a polynomial is prime is crucial in algebra. It prevents unnecessary time spent trying to factor expressions that are, in fact, unfactorable in the set of real numbers. Always calculate the discriminant first to save time and effort.