# Homework Help: Determine whether the function f(x) is continuous

1. Dec 11, 2009

### naspek

1. The problem statement, all variables and given/known data

Given that

f(x) = { x + 1 ...................; if x < 1
........{ 2 .........................; if x = 1
........{ [4(x-1)] / (x^2 - 1) ; if x > 1

Determine whether the function f(x) is continuous at x = 1

i dont know how to start..
can someone give me an idea to start..

2. Dec 11, 2009

### VeeEight

Re: Continuity

Try finding the limit of f as x approaches 1 from the left and the right (that is, with values of x < 1 and values of x > 1)

3. Dec 11, 2009

### naspek

Re: Continuity

ok.. for

$$\lim_{x \to 1^{-}} f(x)$$

i got 0

for

$$\lim_{x \to 1^{+}} f(x)$$

i got 2

am i got it right?
so.. how can i conclude it?

4. Dec 11, 2009

### cap.r

Re: Continuity

ok so now you have to go back to the calc one definition of continuity. the requirements were
If f is continuous at a then, these 3 facts have to hold
$$\lim_{x \to a^{-}} f(x) = f(a)$$
$$\lim_{x \to a^{+}} f(x) = f(a)$$
$$\lim_{x \to a} f(x) = f(a)$$

5. Dec 12, 2009

### HallsofIvy

Re: Continuity

For x< 0, f(x)= 1+ x. Are you saying that $\lim_{x\to 0} 1+ x= 0$?

This function is continuous at x=0 only if the limit there exists and is equal to f(0). The limit itself exist only if those two one sided limits are the same.