Find the value of a and b for which the function is continuous at 2

In summary, the conversation discusses finding the values of a and b for which the function u(x) is continuous at x=2. The person attempts to solve the problem by setting the limits equal to each other and using the formula for A^n-B^n. They determine that a=1 and solve for b. However, there is a discrepancy in the limit when x<2 and they ask for clarification on their answer.
  • #1
ilhamGD
4
0

Homework Statement



[tex]
u(x) =
\begin{cases}
\frac{3x+b}{4} & \text{if } x \geq 2 \\
\frac{(3-x)^n-a}{x-2} & \text{if } x < 2
\end{cases}
[/tex]
find the value of a and b for which the function is continuous at 2

The Attempt at a Solution


I tried to proof that lim(3x+b)/4 = lim (3-x)^n-a/x-2 = f(2)
that gives lim (3-x)^n-a/x-2= 6+b/4
But I have a problem with the limit when x< 2, I don't know how to solve it
Can u please help ?
[/B]
 
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  • #2
The difficulty with x< 2 is, of course, that the denominator is 0 at x= 2. In order for that to have a chance at having a limit, the numerator must also be 0 at x= 2. That is, we must have [tex](3- 2)^n- a[/tex]. What does that tell you about a?
 
  • #3
It means that a=1, and after using the formula for A^n-B^n the limit when x< 2 becomes -(2^n-1+2^n-2+...+1) which is -2^(n-2) and then I can find b which is -2^(n-1)/3
can u tell me if that is correct ? and should I also find f(2)?
 
  • #4
ilhamGD said:
It means that a=1, and after using the formula for A^n-B^n the limit when x< 2 becomes -(2^n-1+2^n-2+...+1) which is -2^(n-2) and then I can find b which is -2^(n-1)/3
can u tell me if that is correct ? and should I also find f(2)?
I don't get the same answer for that limit. Please post your detailed working.
 

1. What does it mean for a function to be continuous at a specific point?

A function is considered continuous at a specific point if the function exists at that point, the limit of the function at that point exists, and the limit and the function value at that point are equal.

2. How can we determine the value of a and b for which the function is continuous at 2?

We can determine the value of a and b by setting up an equation that satisfies the conditions for continuity at 2. This includes ensuring that the function exists at 2, the limit of the function at 2 exists, and the limit and the function value at 2 are equal. We can then solve for a and b using algebraic methods.

3. What is the importance of a function being continuous at a point?

A function being continuous at a point means that there are no breaks or jumps in the graph at that point. This is important because it allows us to make accurate predictions and calculations using the function, as well as make connections between different parts of the function.

4. Are there any specific methods for finding the values of a and b for continuity at 2?

Yes, there are specific methods such as using the definition of continuity, using the intermediate value theorem, or using the properties of continuity to solve for a and b. It ultimately depends on the specific function and the given conditions.

5. Can a function be continuous at a point if it is not defined at that point?

No, a function cannot be continuous at a point if it is not defined at that point. In order for a function to be continuous at a point, it must exist at that point.

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