Post

Created by @nathanedwards
 at November 3rd 2023, 3:46:52 pm.

Question:

Consider the function

f(x)={x21x1if x12if x=1 f(x) = \begin{cases} \dfrac{x^2 - 1}{x - 1} & \text{if } x \neq 1 \\ 2 & \text{if } x = 1 \end{cases}
  1. Determine the values of aa and bb for which the function f(x)f(x) is continuous at x=1x = 1.
  2. Identify and classify any other types of discontinuities (removable, jump, infinite) for the function f(x)f(x).

Answer:

To determine the values of aa and bb for which the function f(x)f(x) is continuous at x=1x = 1, we need to check if the following conditions are met:

  1. The limit of f(x)f(x) as xx approaches 1 from the left side is equal to the limiting value as xx approaches 1 from the right side.
  2. The limiting value as xx approaches 1 from either side is equal to the value of f(x)f(x) at x=1x = 1.

Let's begin by finding the limit of f(x)f(x) as xx approaches 1 from the left side, denoted as L1L_1:

L1=limx1f(x) L_1 = \lim_{x \to 1^-} f(x)

Substituting the given function:

L1=limx1x21x1 L_1 = \lim_{x \to 1^-} \dfrac{x^2 - 1}{x - 1}

We can simplify the expression using algebraic manipulation:

L1=limx1(x+1)(x1)x1 L_1 = \lim_{x \to 1^-} \dfrac{(x+1)(x-1)}{x - 1}

Since both the numerator and denominator have common factors of (x1)(x-1), we can cancel them:

L1=limx1(x+1) L_1 = \lim_{x \to 1^-} (x+1)

Now, we can evaluate the limit:

L1=1+1=2 L_1 = 1 + 1 = 2

Next, let's find the limit of f(x)f(x) as xx approaches 1 from the right side, denoted as L2L_2:

L2=limx1+f(x) L_2 = \lim_{x \to 1^+} f(x)

Substituting the given function:

L2=limx1+x21x1 L_2 = \lim_{x \to 1^+} \dfrac{x^2 - 1}{x - 1}

Again, we can simplify the expression using algebraic manipulation:

L2=limx1+(x+1)(x1)x1 L_2 = \lim_{x \to 1^+} \dfrac{(x+1)(x-1)}{x - 1}

Cancelling the common factors:

L2=limx1+(x+1) L_2 = \lim_{x \to 1^+} (x+1)

Evaluating the limit:

L2=1+1=2 L_2 = 1 + 1 = 2

Since both L1=2L_1 = 2 and L2=2L_2 = 2, we can conclude that the function f(x)f(x) is continuous at x=1x = 1 if a=b=2a = b = 2.

Now, let's examine other types of discontinuities for the function f(x)f(x).

To determine if there are any removable discontinuities, we need to check if the function can be redefined at certain points to make it continuous. In this case, f(x)f(x) is already continuous at x=1x = 1, so there are no removable discontinuities.

To identify jump discontinuities, we look for abrupt changes in the value of the function as xx approaches a specific point. Since we have already established the continuity at x=1x = 1, there are no jump discontinuities for f(x)f(x).

Lastly, we check for infinite discontinuities by looking for vertical asymptotes. We observe that the function is a rational expression, and there is a potential vertical asymptote if the denominator becomes zero. In this case, as xx approaches 11, the denominator x1x - 1 becomes zero. Thus, we have a vertical asymptote at x=1x = 1.

To summarize, for the function f(x)f(x):

  • The function is continuous at x=1x = 1 if a=b=2a = b = 2.
  • There are no removable discontinuities.
  • There are no jump discontinuities.
  • There is a vertical asymptote at x=1x = 1.