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What is the sum of the rational expressions below?

[tex]\[ \frac{x}{x+1}+\frac{6x}{x+5} \][/tex]

A. [tex]\[ \frac{7x}{2x+6} \][/tex]

B. [tex]\[ \frac{7x^2+11x}{x^2+6x+5} \][/tex]

C. [tex]\[ \frac{7x}{x^2+6x+5} \][/tex]

D. [tex]\[ \frac{7x^2+11x}{2x+6} \][/tex]


Sagot :

To find the sum of the rational expressions [tex]\(\frac{x}{x+1} + \frac{6x}{x+5}\)[/tex], we need to follow these steps:

1. Find the common denominator:

Identify the denominators of the two rational expressions:
[tex]\[ x + 1 \quad \text{and} \quad x + 5 \][/tex]

The common denominator is the product of these two denominators:
[tex]\[ (x + 1)(x + 5) \][/tex]

2. Rewrite each fraction with the common denominator:

For [tex]\(\frac{x}{x+1}\)[/tex], multiply both the numerator and denominator by [tex]\((x + 5)\)[/tex]:
[tex]\[ \frac{x \cdot (x + 5)}{(x+1)(x+5)} \][/tex]
This gives:
[tex]\[ \frac{x(x + 5)}{(x+1)(x+5)} = \frac{x^2 + 5x}{(x+1)(x+5)} \][/tex]

For [tex]\(\frac{6x}{x+5}\)[/tex], multiply both the numerator and denominator by [tex]\((x + 1)\)[/tex]:
[tex]\[ \frac{6x \cdot (x + 1)}{(x+5)(x+1)} \][/tex]
This gives:
[tex]\[ \frac{6x(x + 1)}{(x+5)(x+1)} = \frac{6x^2 + 6x}{(x+5)(x+1)} \][/tex]

3. Add the fractions:

Combine the fractions by adding their numerators over the common denominator:
[tex]\[ \frac{x^2 + 5x}{(x+1)(x+5)} + \frac{6x^2 + 6x}{(x+1)(x+5)} = \frac{x^2 + 5x + 6x^2 + 6x}{(x+1)(x+5)} \][/tex]

4. Combine like terms in the numerator:

[tex]\[ x^2 + 5x + 6x^2 + 6x = 7x^2 + 11x \][/tex]

5. Write the final sum:

The sum of the rational expressions is:
[tex]\[ \frac{7x^2 + 11x}{(x+1)(x+5)} \][/tex]

The common denominator can be expanded:
[tex]\[ (x+1)(x+5) = x^2 + 6x + 5 \][/tex]
Therefore, the final sum is:
[tex]\[ \frac{7x^2 + 11x}{x^2 + 6x + 5} \][/tex]

Thus, the correct answer is:
[tex]\[ \boxed{\frac{7x^2 + 11x}{x^2 + 6x + 5}} \quad \text{which corresponds to option} \quad \text{B} \][/tex]