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If [tex]f(x) = 2x^2 - 5[/tex] and [tex]g(x) = x^2 - 4x - 8[/tex], find [tex](f - g)(x)[/tex].

A. [tex](f - g)(x) = x^2 - 4x - 3[/tex]

B. [tex](f - g)(x) = x^2 + 4x + 3[/tex]

C. [tex](f - g)(x) = -x^2 - 13[/tex]

D. [tex](f - g)(x) = 3x^2 - 4x - 13[/tex]


Sagot :

To find \((f - g)(x)\) for the given functions \(f(x)\) and \(g(x)\), we perform the following steps:

1. Write down the given functions:
[tex]\[ f(x) = 2x^2 - 5 \][/tex]
[tex]\[ g(x) = x^2 - 4x - 8 \][/tex]

2. Subtract \(g(x)\) from \(f(x)\):

[tex]\[ (f - g)(x) = f(x) - g(x) \][/tex]

Substituting the expressions for \(f(x)\) and \(g(x)\), we get:
[tex]\[ (f - g)(x) = (2x^2 - 5) - (x^2 - 4x - 8) \][/tex]

3. Distribute the negative sign and combine like terms:
[tex]\[ (f - g)(x) = 2x^2 - 5 - x^2 + 4x + 8 \][/tex]

4. Simplify the expression by combining like terms:
- Combine the \(x^2\) terms:
[tex]\[ 2x^2 - x^2 = x^2 \][/tex]
- The \(x\) terms remain as is:
[tex]\[ +4x \][/tex]
- Combine the constant terms:
[tex]\[ -5 + 8 = 3 \][/tex]

So, the simplified expression is:
[tex]\[ (f - g)(x) = x^2 + 4x + 3 \][/tex]

5. Check the multiple-choice options:
- A. \(x^2 - 4x - 3\)
- B. \(x^2 + 4x + 3\)
- C. \(-x^2 - 13\)
- D. \(3x^2 - 4x - 13\)

The correct expression \((f - g)(x)\) which we found is \(x^2 + 4x + 3\).

Thus, the correct answer is:
[tex]\[ \boxed{B} \][/tex]