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## Homework Statement

Demonstrate if A

_{1}⊂ A

_{2}→ƒ(A

_{1}) ⊂ ƒ(A

_{2})

2. Homework Equations

2. Homework Equations

ƒ:A→B is a map

A

_{1}, A

_{2}⊂ A

## The Attempt at a Solution

first assumed that (A

_{1}∪A

_{2})⊆A

⇒ (ƒ(A

_{1}) ∪ ƒ(A

_{2}))⊆ ƒ(A)

then if A

_{1}⊂ A

_{2}

∴ ƒ(A

_{1}) ⊂ ƒ(A

_{1})

I don't know if this demonstration is satisfying enough. I'm missing something related to properties of a function.