The functions [tex]\( f(x) \)[/tex] and [tex]\( g(x) \)[/tex] are defined below.

[tex]\[
\begin{array}{l}
f(x)=\frac{x-16}{x^2+6x-40}, \text{ for } x \neq -10 \text{ and } x \neq 4 \\
g(x)=\frac{1}{x+10}, \text{ for } x \neq -10
\end{array}
\][/tex]

Which expression is equal to [tex]\( f(x) + g(x) \)[/tex]?

A. [tex]\(\frac{x-15}{x^2+7x-30}\)[/tex]

B. [tex]\(\frac{x-15}{x^2+6x-40}\)[/tex]

C. [tex]\(\frac{2x-20}{x^2+6x-40}\)[/tex]

D. [tex]\(\frac{2x-12}{x^2+6x-40}\)[/tex]



Answer :

To solve for the expression [tex]\( f(x) + g(x) \)[/tex], let's follow these steps:

We start with the given functions:
[tex]\[ f(x) = \frac{x-16}{x^2 + 6x - 40} \][/tex]
[tex]\[ g(x) = \frac{1}{x+10} \][/tex]

### Step 1: Find a Common Denominator

To add these two fractions, [tex]\( f(x) \)[/tex] and [tex]\( g(x) \)[/tex], we need a common denominator. The denominators are:
[tex]\[ x^2 + 6x - 40 \][/tex] and [tex]\[ x + 10 \][/tex]

The common denominator will be the product of these two expressions:
[tex]\[ (x^2 + 6x - 40)(x + 10) \][/tex]

### Step 2: Rewrite Each Fraction with the Common Denominator

Next, we rewrite both fractions with this common denominator.

#### For [tex]\( f(x) \)[/tex]:
The numerator of [tex]\( f(x) \)[/tex] needs to be adjusted by multiplying it by [tex]\( x + 10 \)[/tex]:
[tex]\[ f(x) = \frac{(x - 16)(x + 10)}{(x^2 + 6x - 40)(x + 10)} \][/tex]

#### For [tex]\( g(x) \)[/tex]:
The numerator of [tex]\( g(x) \)[/tex] needs to be adjusted by multiplying it by [tex]\( x^2 + 6x - 40 \)[/tex]:
[tex]\[ g(x) = \frac{1 \cdot (x^2 + 6x - 40)}{(x + 10)(x^2 + 6x - 40)} \][/tex]

### Step 3: Add the Fractions

With the common denominator established, add the fractions by summing their numerators:

[tex]\[ \frac{(x - 16)(x + 10) + (x^2 + 6x - 40)}{(x^2 + 6x - 40)(x + 10)} \][/tex]

### Step 4: Simplify the Numerator

First, expand [tex]\((x - 16)(x + 10)\)[/tex]:
[tex]\[ (x - 16)(x + 10) = x^2 + 10x - 16x - 160 = x^2 - 6x - 160 \][/tex]

Now, add this result to [tex]\( (x^2 + 6x - 40) \)[/tex]:
[tex]\[ x^2 - 6x - 160 + x^2 + 6x - 40 \][/tex]

Combine like terms:
[tex]\[ = 2x^2 - 200 \][/tex]

### Step 5: Write the Sum

We now have:
[tex]\[ f(x) + g(x) = \frac{2x^2 - 200}{(x^2 + 6x - 40)(x + 10)} \][/tex]

### Step 6: Simplify the Result

To match the form of the given options, factor out a common term in the numerator:
[tex]\[ 2x^2 - 200 = 2(x^2 - 100) = 2(x - 10)(x + 10) \][/tex]

This can simplify to:
[tex]\[ \frac{2(x - 10)(x + 10)}{(x^2 + 6x - 40)(x + 10)} \][/tex]

Cancel out the common factor [tex]\((x + 10)\)[/tex] in the numerator and denominator:
[tex]\[ \frac{2(x - 10)}{x^2 + 6x - 40} \][/tex]

Thus, the final simplified form of [tex]\( f(x) + g(x) \)[/tex] is:
[tex]\[ \frac{2x - 20}{x^2 + 6x - 40} \][/tex]

### Step 7: Compare with the Given Options

From the obtained simplified expression:
[tex]\[ \frac{2x - 20}{x^2 + 6x - 40} \][/tex]

We see that it matches Option C:
[tex]\[ \frac{2x - 20}{x^2 + 6x - 40} \][/tex]

Therefore, the correct expression equal to [tex]\( f(x) + g(x) \)[/tex] is:
[tex]\[ \boxed{C} \][/tex]