Question

Evaluate \(\sqrt{b^{2}-4 a c}\) for the given values. $$a=6, b=-8, c=4$$

Short answer

The discriminant \(\sqrt{b^{2}-4ac}\) for values \(a=6\), \(b=-8\), and \(c=4\) does not have a real number solution because it would require taking the square root of a negative number.

Step-by-step solution

Understand the formula

Discriminant is given by the formula \(\sqrt{b^{2}-4ac}\) for a quadratic equation with coefficients a, b and c.

Substitute the values into the formula

Substitute the given values \(a=6\), \(b=-8\), and \(c=4\) into the formula. That gives us \(\sqrt{(-8)^{2} - 4 * 6 * 4}\).

Calculate the squares and the multiplication

First, calculate the square of -8, which is \((-8)^2 = 64\). Then calculate 4*6*4 = 96.

Subtract to get the discriminant

Now subtract: 64 - 96 = -32. But we're evaluating the square root, and this doesn't have a real number solution.

Key concepts

Quadratic Equation

The quadratic equation is a second-degree polynomial of the form \( ax^2 + bx + c = 0 \), where \(a\), \(b\), and \(c\) are coefficient constants, with \(a \eq 0\). These equations are fundamental in algebra and are used to model various physical phenomena, such as projectile motion.

Understanding the relationships between the coefficients and the roots—solutions to the equation—is key to solving quadratic equations. The solutions for \(x\) can be real or complex and can be distinct, repeated, or even complex conjugates, depending on the nature of the discriminant, \( \sqrt{b^2 - 4ac} \).

When tackling these equations, one important concept to keep in mind is that the sign of the discriminant provides valuable information regarding the nature of the roots: a positive discriminant implies two distinct real roots, zero discriminant corresponds to a single repeated real root, and a negative discriminant indicates two distinct complex roots.

Quadratic Formula

The quadratic formula is a reliable method for finding the roots of a quadratic equation. It is stated as: \[ x = \frac{{-b \pm \sqrt{b^2 - 4ac}}}{{2a}} \].

This formula provides a step-by-step solution for the roots of any quadratic equation by directly substituting the coefficients \(a\), \(b\), and \(c\). The symbol \(\pm\) indicates that there will be two solutions for \(x\), one for \(+\) and another for \(–\). The expression under the square root, \(b^2 - 4ac\), is known as the discriminant, which plays a crucial role in determining the type and number of roots.

Using the quadratic formula is straightforward and involves these steps: calculating the discriminant, determining its nature (positive, zero, or negative), and then computing the actual roots based on this information. The formula encapsulates the relationship between the coefficients and the roots in one neat expression and ensures you can solve any quadratic equation, given its coefficients are real numbers.

Complex Numbers

Complex numbers extend the idea of quantity beyond the real numbers. A complex number is composed of a real part and an imaginary part and is represented as \(a + bi\), where \(a\) is the real part, \(b\) is the imaginary part, and \(i\) is the imaginary unit defined by \(i^2 = -1\).

When the discriminant of a quadratic equation is negative, as in the given exercise \( \sqrt{-32} \), the roots of the equation are complex numbers. This happens because the square root of a negative number isn't defined within the system of real numbers. By introducing complex numbers, we can express solutions even when the discriminant is negative.

The square root of a negative number \( \sqrt{-1} \) is denoted by \(i\) which is the fundamental unit of complex numbers. Hence, the square root of \( -32 \) can be written as \( \sqrt{32} \cdot i \), or more simply, \(|4\sqrt{2}i|\). Complex numbers follow the same arithmetical rules as real numbers, and they're essential in various fields of science and engineering, particularly in the study of oscillations and waves.