Pregunta
Write the following expression in factored form. \( x^{2}-2 x-15 \) \( (x+1)(x-15) \) \( (x-1)(x+15) \) \( (x+3)(x-5) \) \( (x-3)(x+5) \)
Ask by Johnson Warner. in the United States
Jan 27,2025
Solución de tutoría real
Respuesta verificada por el tutor
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The factored form of \( x^{2} - 2x - 15 \) is \( (x + 3)(x - 5) \).
Solución
To factor the quadratic expression \( x^{2} - 2x - 15 \), we need to find two numbers that:
1. **Multiply to** the constant term (**-15**).
2. **Add up to** the coefficient of the middle term (**-2**).
Let's identify these numbers step by step:
1. **Find factors of -15:**
- \( 1 \) and \( -15 \) → \( 1 \times (-15) = -15 \) and \( 1 + (-15) = -14 \)
- \( -1 \) and \( 15 \) → \( -1 \times 15 = -15 \) and \( -1 + 15 = 14 \)
- \( 3 \) and \( -5 \) → \( 3 \times (-5) = -15 \) and \( 3 + (-5) = -2 \)
2. **Select the pair that adds up to -2:**
- The pair **\( 3 \) and \( -5 \)** satisfy both conditions.
3. **Write the factored form:**
\[
x^{2} - 2x - 15 = (x + 3)(x - 5)
\]
**Among the given options:**
- \( (x+1)(x-15) \)
- \( (x-1)(x+15) \)
- \( (x+3)(x-5) \) ✅ **Correct**
- \( (x-3)(x+5) \)
**Therefore, the correct factored form is:**
\[
(x + 3)(x - 5)
\]
Revisado y aprobado por el equipo de tutoría de UpStudy
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The Deep Dive
To factor the expression \( x^{2}-2x-15 \), we need to find two numbers that multiply to \(-15\) (the constant term) and add to \(-2\) (the coefficient of \(x\)). The numbers \(-5\) and \(3\) fit this requirement because \(-5 \times 3 = -15\) and \(-5 + 3 = -2\). Therefore, we can factor the expression as \( (x - 5)(x + 3) \). Now, remember to check your work! One common mistake is to overlook the signs. Always ensure that the signs of the factors align with the product and sum needed to match the original quadratic.
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