Thorem: If f(x) is continuous at L and lim_(x->a) g(x)=L, then lim_(x->a) f(g(x)=f(lim_(x->a) g(x))=f(L). Proof: Assume f(x) is continuous at a point L, and that lim_(x->a) g(x)=L.

Modelfino0g

Modelfino0g

Answered question

2022-09-14

Thorem: If f ( x ) is continuous at L and lim x a g ( x ) = L, then lim x a f ( g ( x ) = f ( lim x a g ( x ) ) = f ( L ).
Proof: Assume f ( x ) is continuous at a point L, and that lim x a g ( x ) = L.
ϵ > 0 , δ > 0 : [ | x L | < δ | f ( x ) f ( L ) | < ε ].
And δ > 0 , δ > 0 : [ | x a | < δ | g ( x ) L < δ ].
So, δ > 0 , δ > 0 : [ | x a | < δ | f ( g ( x ) ) f ( L ) | < ϵ ].
lim x a g ( x ) = L so f ( lim x a g ( x ) ) = f ( L ).

Answer & Explanation

wegpluktee3

wegpluktee3

Beginner2022-09-15Added 12 answers

You're doing the right thing but the way you've presented it is a bit confusing. Why not word it like this:
Pick ϵ > 0. Continuity of f at L gives you an η such that | x L | < η | f ( x ) f ( L ) | < ϵ.
For this η, lim x a g ( x ) = L gives you a δ such that | x a | < δ | g ( x ) L | < η.
Hence | x a | < δ | g ( x ) L | < η | f ( g ( x ) ) f ( L ) | < ϵ

Do you have a similar question?

Recalculate according to your conditions!

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?