Proving Continuity for Composition of Functions: f(x,y)=g(x)

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SUMMARY

The discussion focuses on proving the continuity of the function f(x,y) = g(x) at the point (a,b) for all b in R, given that g: R -> R is continuous at a. The key argument presented is that for every ε > 0, there exists a δ > 0 such that if |x - a| < δ, then |g(x) - g(a)| < ε. The participant suggests substituting g(x) and g(a) into the continuity condition but questions the validity of their approach regarding the distance condition |(x,y) - (a,b)| < δ. The correct interpretation emphasizes that if |(x,y) - (a,b)| < δ, then |x - a| can be appropriately bounded.

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Homework Statement



Prove that if g:R->R is continuous at a then f(x,y)=g(x) is continuous at (a,b) \forall b \in R

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The Attempt at a Solution



So we know
\foralle>0 \existsd>0 s.t. \forallx\inR where |x-a|<d we have |g(x) - g(a)|<e
So I've said as \forallb\inR g(x)=f(x,y) & g(a)=f(a,b), these can be substituted in giving the expression we need except for the condition that [(x-a)2 + (y-b)2]1/2<d.
This seems to be an incorrect cheat though, am I along the right lines or not?
 
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You are looking at the right line of thought.If |(x,y)-(a,b)|<d, what can you say about |x-a|?
 

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