F of x equals 2x squared- x - 6

Gof x equals x squared+ 3x - 10
What is f over g of X then find the domain of f over g of X

1 answer

To find \( \frac{f}{g}(x) \), we first need to express \( f(x) \) and \( g(x) \):

  • \( f(x) = 2x^2 - x - 6 \)
  • \( g(x) = x^2 + 3x - 10 \)

Step 1: Calculate \( \frac{f}{g}(x) \)

\[ \frac{f}{g}(x) = \frac{f(x)}{g(x)} = \frac{2x^2 - x - 6}{x^2 + 3x - 10} \]

Step 2: Factor \( f(x) \) and \( g(x) \)

Factoring \( f(x) \):

To factor \( 2x^2 - x - 6 \), we need two numbers that multiply to \( 2 \cdot (-6) = -12 \) and add to \(-1\). The numbers \(-4\) and \(3\) work.

\[ f(x) = 2x^2 - 4x + 3x - 6 = 2x(x - 2) + 3(x - 2) = (2x + 3)(x - 2) \]

Factoring \( g(x) \):

To factor \( x^2 + 3x - 10 \), we need two numbers that multiply to \(-10\) and add to \(3\). The numbers \(5\) and \(-2\) work.

\[ g(x) = x^2 + 5x - 2x - 10 = (x + 5)(x - 2) \]

Step 3: Rewrite \( \frac{f}{g}(x) \)

Using the factored forms:

\[ \frac{f}{g}(x) = \frac{(2x + 3)(x - 2)}{(x + 5)(x - 2)} \]

We can simplify this fraction:

\[ \frac{f}{g}(x) = \frac{2x + 3}{x + 5}, \quad \text{for } x \neq 2 \]

Step 4: Determine the Domain of \( \frac{f}{g}(x) \)

The domain of \( \frac{f}{g}(x) \) is all \( x \) values for which \( g(x) \) is not zero.

To find where \( g(x) = 0 \):

Set \( g(x) = x^2 + 3x - 10 = 0 \). Factoring gives:

\[ (x + 5)(x - 2) = 0 \]

This gives the roots:

  • \( x + 5 = 0 \) ⇒ \( x = -5 \)
  • \( x - 2 = 0 \) ⇒ \( x = 2 \)

Thus, \( g(x) \) is zero at \( x = -5 \) and \( x = 2 \).

Therefore, the domain of \( \frac{f}{g}(x) \) is:

\[ \text{Domain: } x \in \mathbb{R} \text{, where } x \neq -5 \text{ and } x \neq 2. \]

In interval notation, the domain is:

\[ (-\infty, -5) \cup (-5, 2) \cup (2, \infty) \]