Chapter 8: Problem 21
Solve. (Find all complex-number solutions.) \(p^{2}-p+1=0\)
Short Answer
Expert verified
The solutions are \( p = \frac{1 + i\sqrt{3}}{2} \) and \( p = \frac{1 - i\sqrt{3}}{2} \).
Step by step solution
01
Identify the quadratic equation
The given problem is a quadratic equation in the form of \[ p^{2} - p + 1 = 0 \]
02
Use the Quadratic Formula
To find the solutions of the quadratic equation \( ax^{2} + bx + c = 0 \), we use the quadratic formula: \[ p = \frac{-b \pm \sqrt{b^{2} - 4ac}}{2a} \]. Here, \( a = 1 \), \( b = -1 \), and \( c = 1 \).
03
Calculate the Discriminant
The discriminant of a quadratic equation is \( b^{2} - 4ac \). Substitute \( a = 1 \), \( b = -1 \), and \( c = 1 \) into the discriminant formula: \( (-1)^{2} - 4(1)(1) = 1 - 4 = -3 \). The discriminant is \( -3 \).
04
Find the Complex Solutions
Since the discriminant is negative, the equation has two complex solutions. Use the quadratic formula to find them: \[ p = \frac{-b \pm \sqrt{b^{2} - 4ac}}{2a} \]. Substituting the values, we get: \[ p = \frac{-(-1) \pm \sqrt{-3}}{2(1)} = \frac{1 \pm \sqrt{-3}}{2} \]. Recall that \( \sqrt{-3} = i \sqrt{3} \). So the solutions are: \[ p = \frac{1 + i\sqrt{3}}{2} \] and \[ p = \frac{1 - i\sqrt{3}}{2} \].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
quadratic equation
A quadratic equation is a polynomial equation of degree 2. In a general form, it looks like this:
\[ ax^2 + bx + c = 0 \]
where:
\[ p^2 - p + 1 = 0 \]
is a quadratic equation because the highest power of the variable, p, is 2.
\[ ax^2 + bx + c = 0 \]
where:
- a, b, and c are constants
- x is the variable
\[ p^2 - p + 1 = 0 \]
is a quadratic equation because the highest power of the variable, p, is 2.
quadratic formula
The quadratic formula is a tool used to find the solutions of a quadratic equation. It works for any quadratic equation, whether the solutions are real or complex. The formula is:
\[ p = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]
To use the quadratic formula, you plug in the values of a, b, and c from your quadratic equation. For example, in the equation \[ p^2 - p + 1 = 0 \], we have:
\[ p = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]
To use the quadratic formula, you plug in the values of a, b, and c from your quadratic equation. For example, in the equation \[ p^2 - p + 1 = 0 \], we have:
- a = 1
- b = -1
- c = 1
discriminant
The discriminant is part of the quadratic formula that helps determine the nature of the solutions. It's given by:
\[ b^2 - 4ac \]
The value of the discriminant tells us if the solutions are real or complex:
\[ (-1)^2 - 4(1)(1) = 1 - 4 = -3 \].
Since the discriminant is -3, the equation has two complex solutions.
\[ b^2 - 4ac \]
The value of the discriminant tells us if the solutions are real or complex:
- If the discriminant is positive (>0), the quadratic equation has two distinct real solutions.
- If the discriminant is zero (=0), the quadratic equation has one real solution (also called a repeated root).
- If the discriminant is negative (<0), the quadratic equation has two complex solutions.
\[ (-1)^2 - 4(1)(1) = 1 - 4 = -3 \].
Since the discriminant is -3, the equation has two complex solutions.
complex numbers
Complex numbers are numbers that have both a real part and an imaginary part. They are written in the form:
\[ a + bi \]
where:
\[ p = \frac{1 \pm \sqrt{-3}}{2} \]
To express these as complex numbers, we use the fact that \( \sqrt{-1} = i \). Thus, \( \sqrt{-3} = i \sqrt{3} \), and the solutions become:
\[ p = \frac{1 + i\sqrt{3}}{2} \]
and
\[ p = \frac{1 - i\sqrt{3}}{2} \].
These are the complex-number solutions to our quadratic equation.
\[ a + bi \]
where:
- a is the real part
- bi is the imaginary part, with i representing the imaginary unit \( \sqrt{-1} \)
\[ p = \frac{1 \pm \sqrt{-3}}{2} \]
To express these as complex numbers, we use the fact that \( \sqrt{-1} = i \). Thus, \( \sqrt{-3} = i \sqrt{3} \), and the solutions become:
\[ p = \frac{1 + i\sqrt{3}}{2} \]
and
\[ p = \frac{1 - i\sqrt{3}}{2} \].
These are the complex-number solutions to our quadratic equation.