The conjugate of a + bi is a − bi. Their product is a² + b², a real number, which is how you clear a complex denominator. Complex numbers as a set are in complex numbers.
Multiply by the twin
(3 + 2i)(3 − 2i) = 9 − (2i)² = 9 − (−4) = 13. i² is −1, in i squared. Matrix addition is a different leftover skill, in matrix addition.
The short list is in ACT Math formulas.
The bottom line
Flip the sign on the imaginary part. Product is a² + b².
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