Last updated on Oct 23, 2026

Multiplying (Leaving Cert Mathematics): Flashcards

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Multiplying

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Method to multiply complex numbers

Expand brackets, replace $i^2=-1$

Value of $i^2$

$-1$

$(2-3i)(2+4i)$ equals

$16+2i$

Simplify $-12i^2$

$12$

Are complex numbers commutative under multiplication?

Yes, $zw = wz$

Associative property for complex multiplication

$u(zw) = (uz)w$

First step when multiplying complex numbers

Expand brackets as usual

When to replace $i^2=-1$ in complex multiplication

Where applicable after expanding

Term from $(2)(4i)$ in expansion

$8i$

Term from $(-3i)(2)$ in expansion

$-6i$

Combine imaginary terms: $8i-6i$

$2i$

Combine real terms: $4+12$ in example

$16$

Complex multiplication follows rules similar to?

Real numbers

Step after expanding, before combining like terms

Replace $i^2$ with $-1$

Explore Leaving Cert Mathematics Revision Notes by Topics

Fundamentals of Complex Numbers

The Basics

Argand Diagrams & Modulus

Solving Equations

DeMoivre's Theorem

Transformations

Explore Leaving Cert Mathematics Model Answers by Topics

Fundamentals of Complex Numbers

The Basics

Argand Diagrams & Modulus

Solving Equations

DeMoivre's Theorem

Transformations

Explore Leaving Cert Mathematics Quizzes by Topics

Fundamentals of Complex Numbers

The Basics

Argand Diagrams & Modulus

Solving Equations

DeMoivre's Theorem

Transformations

Explore Leaving Cert Mathematics Exam Questions by Topics

Fundamentals of Complex Numbers

The Basics

Argand Diagrams & Modulus

Solving Equations

DeMoivre's Theorem

Transformations

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