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Math

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PROBLEM

Find the xx-values (if any) at which ff is not continuous. State whether the discontinuities are removable or nonremovable. (Enter your answers as comma-separated lists. If an answer does not exist, enter DNE.)
f(x)=x+2x22x8f(x)=\frac{x+2}{x^{2}-2 x-8} removable discontinuities
x=x= \square
nonremovable discontinuities x=\quad x= \square

STEP 1

What is this asking?
We're looking for any x-values where the function f(x)f(x) has a discontinuity, and then we need to classify each discontinuity as either removable or nonremovable.
Watch out!
Remember, a discontinuity is removable if we can "fill in the hole" by defining the function at that point.
Nonremovable discontinuities are like asymptotes where the function explodes!

STEP 2

1. Simplify the Function
2. Find Potential Discontinuities
3. Classify the Discontinuities

STEP 3

Let's factor the denominator of our function f(x)f(x).
We're doing this because factoring helps us see if there are any common factors between the numerator and denominator, which might lead to removable discontinuities.
f(x)=x+2x22x8f(x) = \frac{x+2}{x^2 - 2x - 8} f(x)=x+2(x4)(x+2)f(x) = \frac{x+2}{(x-4)(x+2)}

STEP 4

Now, we see a common factor of (x+2)(x+2) in both the numerator and the denominator!
We can simplify f(x)f(x) by dividing both by (x+2)(x+2).
Remember, we can only do this if x+20x+2 \ne 0, which means x2x \ne -2.
So, for x2x \ne -2, we have:
f(x)=1x4f(x) = \frac{1}{x-4} This simplified form will help us analyze the discontinuities.

STEP 5

From the simplified form, f(x)=1x4f(x) = \frac{1}{x-4}, we see that the function is undefined when the denominator is zero.
This happens when x4=0x-4=0, so x=4x=4.
This is a potential discontinuity.

STEP 6

We also need to consider the value we excluded earlier, x=2x = -2.
Since the original function was undefined at x=2x = -2, this is another potential discontinuity.

STEP 7

Let's look at x=4x = 4.
As xx approaches 4, the function f(x)=1x4f(x) = \frac{1}{x-4} blows up!
It approaches positive infinity from the right and negative infinity from the left.
This is a nonremovable discontinuity, specifically a vertical asymptote.

STEP 8

Now, let's consider x=2x = -2.
In the simplified form, f(x)=1x4f(x) = \frac{1}{x-4}, we can plug in x=2x = -2 and get f(2)=124=16=16f(-2) = \frac{1}{-2-4} = \frac{1}{-6} = -\frac{1}{6}.
Since we can "fill in the hole" at x=2x = -2 by defining f(2)=16f(-2) = -\frac{1}{6}, this is a removable discontinuity.

SOLUTION

Removable discontinuities: x=2x = -2
Nonremovable discontinuities: x=4x = 4

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