Conjugates and Rationalization

In mathematics, a conjugate refers to a pair of expressions that differ only in the sign between their terms. Conjugates are used to simplify expressions, especially when dealing with radicals or complex numbers.

Rationalization is the process of eliminating irrational numbers or complex numbers from the denominator of a fraction. This is done by multiplying both the numerator and denominator by a suitable expression that removes the radical or imaginary part from the denominator.

The conjugate of a surd is a binomial expression involving irrational numbers. E.g., the conjugate of surd x + yz is x - yz and vice versa. The given table will show you the surd and the conjugate of the given surd:
 

To write the conjugate of a complex number, simply change the sign of the imaginary part and retain the real part. For e.g., the conjugate of x + yi is x - yi. The following table will show some complex numbers and their conjugates:

 

The product of a surd and its conjugate is rational. Students can get confused between a conjugate and rational factor. But there is a small difference that helps us determine which is which. The sum of a binomial and its rational factor isn’t always a rational number, but the sum of a binomial and its conjugate is always rational.

The steps involved in rationalizing a single-term denominator are as follows:

Step 1: Identify the radical in the denominator.

Step 2: Use the same radical to multiply both the numerator and denominator. 

Step 3: Simplify the denominator.

The steps involved in rationalizing a two-term denominator are as follows:

Step 1: Identify the denominator and its conjugate.

Step 2: Now that we know the conjugate, we can use it to multiply both the numerator and the denominator.

Step 3: Apply the difference of squares formula.

Step 4: Distribute the numerator.

Step 5: Write the simplified fraction.

Step 6: Simplify further if possible.

The steps involved in rationalizing a three-term denominator are as follows:

Step 1: Group the radical terms and find a suitable conjugate.

Step 2: We can now use the conjugate and multiply both the numerator and the denominator with it.

Step 3: Expand the denominator using distributive property.

Step 4: Apply the difference of squares and remove the radical.

Step 5: Multiply again by the conjugate (only if needed) to fully eliminate radicals.

Step 6: Simplify further if possible.

Conjugates and rationalization has numerous applications across various fields. Let us explore how the conjugates and rationalization is used in different areas:
 

• Engineering and Physics Calculations
  
  In physics and engineering, especially in wave mechanics and signal processing, complex numbers and their conjugates are used to simplify calculations involved in studying oscillations, vibrations and electrical circuits.
   

• Computer Graphics and Animation
  
  Conjugates are important in quaternion algebra, which is used to rotate objects without distortion in animation and 3D graphics. Complex conjugates are used to produce error-free quaternion rotations.
   

• Quantum Mechanics and Wave Functions
  
  In quantum physics, we use complex numbers to indicate wave functions. The product of the wave function and its conjugate is used to calculate the probability density of a quantum.