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Math

Math Snap

PROBLEM

Suppose that the functions gg and hh are defined as follows.
g(x)=x+7h(x)=(x6)(x+6)\begin{array}{l} g(x)=x+7 \\ h(x)=(x-6)(x+6) \end{array} (a) Find (gh)\left(\frac{g}{h}\right) (2).
(b) Find all values that are NOT in the domain of gh\frac{g}{h}.
If there is more than one value, separate them with commas.
(a) (gh)(2)=\left(\frac{g}{h}\right)(2)= \square
(b) Value(s) that are NOT in the domain of gh\frac{g}{h} :

STEP 1

What is this asking?
We've got two functions, g(x)g(x) and h(x)h(x), and we need to figure out what g(x)h(x)\frac{g(x)}{h(x)} is when x=2x = 2, and also what values of xx we can't plug in.
Watch out!
Don't forget: we can't divide by zero!
So, any xx that makes h(x)=0h(x) = 0 is a no-go.

STEP 2

1. Evaluate g(2)
2. Evaluate h(2)
3. Calculate g(2)/h(2)
4. Find the domain of g/h

STEP 3

Let's evaluate g(x)g(x) at x=2x = 2.
We know that g(x)=x+7g(x) = x + 7, so g(2)g(2) is just 2+72 + 7.

STEP 4

g(2)=2+7=9g(2) = 2 + 7 = \textbf{9} So, g(2)=9g(2) = \textbf{9}!

STEP 5

Now let's find h(2)h(2).
We know h(x)=(x6)(x+6)h(x) = (x - 6)(x + 6), so we'll substitute x=2x = 2 into the expression.

STEP 6

h(2)=(26)(2+6)h(2) = (2 - 6)(2 + 6)

STEP 7

h(2)=(4)(8)=-32h(2) = (-4)(8) = \textbf{-32} Great! h(2)=-32h(2) = \textbf{-32}.

STEP 8

Now for the main event: (gh)(2)\left(\frac{g}{h}\right)(2), which is just another way of writing g(2)h(2)\frac{g(2)}{h(2)}.
We already found g(2)=9g(2) = \textbf{9} and h(2)=-32h(2) = \textbf{-32}, so let's put them together!

STEP 9

g(2)h(2)=9-32=932\frac{g(2)}{h(2)} = \frac{\textbf{9}}{\textbf{-32}} = -\frac{9}{32} So, (gh)(2)=932\left(\frac{g}{h}\right)(2) = -\frac{9}{32}!

STEP 10

The domain of gh\frac{g}{h} is all the xx values we can plug in without causing a divide-by-zero error.
Since h(x)h(x) is in the denominator, we need to find any xx values that make h(x)=0h(x) = 0.

STEP 11

We know h(x)=(x6)(x+6)h(x) = (x - 6)(x + 6).
If h(x)=0h(x) = 0, then either (x6)=0(x - 6) = 0 or (x+6)=0(x + 6) = 0.

STEP 12

If x6=0x - 6 = 0, then x=6x = 6.
If x+6=0x + 6 = 0, then x=6x = -6.

STEP 13

So, the values that are not in the domain of gh\frac{g}{h} are x=6x = 6 and x=6x = -6.

SOLUTION

(a) (gh)(2)=932\left(\frac{g}{h}\right)(2) = -\frac{9}{32}
(b) Values not in the domain: 6,66, -6

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