Linear Algebra Done Right · Problem 15

Vector Spaces — Sheldon Axler

Mathematics — Linear Algebra · fn-arithmetic

Problem

Show that (a+b)x=ax+bx(a + b)x = ax + bx for all a,b∈Fa, b \in \mathbf{F} and all x∈Fnx \in \mathbf{F}^n.
Intuitive explanation

This is about verifying that scalar multiplication distributes over addition of scalars—a foundational property of vector spaces. The key is to work component-by-component: expand what (a+b)x(a+b)x means using the definition of scalar multiplication, then show it equals the sum ax+bxax + bx by comparing each coordinate. You're not discovering something deep, but rather confirming that the definition of scalar multiplication respects the field structure of F\mathbf{F}.

Intuitive explanation

This is about verifying that scalar multiplication distributes over addition of scalars—a foundational property of vector spaces. The key is to work component-by-component: expand what (a+b)x(a+b)x means using the definition of scalar multiplication, then show it equals the sum ax+bxax + bx by comparing each coordinate. You're not discovering something deep, but rather confirming that the definition of scalar multiplication respects the field structure of F\mathbf{F}.

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