Conjugate

Definition

A conjugate is a pair of complex numbers or expressions that have the same real part but opposite imaginary parts. The conjugate of a complex number is obtained by changing the sign of the imaginary part, while the real part remains the same. Conjugates play a crucial role in simplifying and manipulating square roots, as well as in other algebraic operations involving complex numbers.

5 Must Know Facts For Your Next Test

1. The conjugate of a complex number $a + bi$ is $a - bi$.
2. Multiplying a complex number by its conjugate results in a real number, as the imaginary parts cancel out.
3. Dividing a complex number by its conjugate is a common technique used to rationalize the denominator and simplify expressions involving square roots.
4. Conjugates are particularly useful in simplifying and manipulating square roots, as they can be used to eliminate the square root symbol.
5. The conjugate of a square root expression, such as $\sqrt{a}$, is the square root expression with the opposite sign, $-\sqrt{a}$.

Review Questions

• Explain how the conjugate of a complex number is obtained and how it is used to simplify expressions involving square roots.
  • The conjugate of a complex number $a + bi$ is obtained by changing the sign of the imaginary part, resulting in $a - bi$. Multiplying a complex number by its conjugate produces a real number, as the imaginary parts cancel out. This property is particularly useful in simplifying expressions involving square roots. For example, to rationalize the denominator of a fraction with a square root in the denominator, you can multiply the numerator and denominator by the conjugate of the square root expression, effectively eliminating the square root symbol.
• Describe the relationship between conjugates and the real and imaginary parts of a complex number. How does this relationship help in performing algebraic operations with complex numbers?
  • The conjugate of a complex number $a + bi$ has the same real part $a$ but the opposite imaginary part $-b$. This relationship between the real and imaginary parts of a complex number and its conjugate is crucial in performing various algebraic operations. For example, when multiplying a complex number by its conjugate, the imaginary parts cancel out, leaving only the real part. This property is used to rationalize denominators and simplify expressions involving square roots. Additionally, the conjugate relationship is used in dividing complex numbers, as dividing by a complex number is equivalent to multiplying by its conjugate.
• Analyze how the concept of conjugates is applied in the context of the topics covered in Sections 9.1 through 9.7, including simplifying and using square roots, multiplying and dividing square roots, and working with higher roots.
  • The concept of conjugates is essential in the topics covered in Sections 9.1 through 9.7. In Section 9.1, conjugates are used to simplify and rationalize expressions involving square roots, as multiplying by the conjugate eliminates the square root symbol. In Section 9.2, conjugates are used to simplify square root expressions by factoring out perfect squares. In Section 9.4, conjugates are used to multiply square root expressions by first multiplying the coefficients and then applying the conjugate relationship to simplify the result. In Section 9.5, conjugates are used to divide square root expressions by first multiplying the numerator and denominator by the conjugate of the denominator, effectively rationalizing the denominator. Finally, in Section 9.7, the concept of conjugates can be extended to higher roots, where similar techniques are used to simplify and manipulate expressions involving higher-order roots.

Related terms

Complex Number: A complex number is a number that can be expressed in the form $a + bi$, where $a$ is the real part and $b$ is the imaginary part.

Imaginary Unit:

The imaginary unit, denoted as $i$, is defined as the square root of $-1$, or $i = \sqrt{-1}$.

Real Part: The real part of a complex number is the coefficient of the $1$ term, or the part of the number that does not involve the imaginary unit $i$.