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Solve the equation by the zero-factor property 6) \( x^{2}+2 x-15=0 \)

Ask by Sullivan Li. in Qatar
Jan 29,2025

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Answer

The solutions are \( x = 3 \) and \( x = -5 \).

Solution

To solve the quadratic equation \( x^{2} + 2x - 15 = 0 \) using the **Zero-Factor Property**, follow these steps: ### Step 1: Factor the Quadratic Equation The Zero-Factor Property states that if the product of two factors is zero, then at least one of the factors must be zero. So, we need to factor the quadratic expression \( x^{2} + 2x - 15 \) into two binomials. **Find two numbers** that: 1. **Multiply to give the constant term (-15).** 2. **Add up to give the coefficient of the middle term (2).** Let's list the pairs of integers that multiply to -15: - \( 1 \) and \( -15 \) (since \( 1 \times (-15) = -15 \)) - \( -1 \) and \( 15 \) (since \( -1 \times 15 = -15 \)) - \( 3 \) and \( -5 \) (since \( 3 \times (-5) = -15 \)) - \( -3 \) and \( 5 \) (since \( -3 \times 5 = -15 \)) Now, identify which pair adds up to **2**: - \( 3 + (-5) = -2 \) ❌ - \( -3 + 5 = 2 \) ✅ So, the numbers are **-3** and **5**. ### Step 2: Write the Factored Form Using the numbers found, factor the quadratic as follows: \[ x^{2} + 2x - 15 = (x - 3)(x + 5) = 0 \] ### Step 3: Apply the Zero-Factor Property Set each factor equal to zero and solve for \( x \): \[ x - 3 = 0 \quad \text{or} \quad x + 5 = 0 \] **Solving these equations:** 1. \( x - 3 = 0 \) \( \Rightarrow x = 3 \) 2. \( x + 5 = 0 \) \( \Rightarrow x = -5 \) ### **Solutions** \[ x = 3 \quad \text{and} \quad x = -5 \] These are the values of \( x \) that satisfy the original equation \( x^{2} + 2x - 15 = 0 \).

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Beyond the Answer

To solve the equation \( x^{2} + 2x - 15 = 0 \) using the zero-factor property, we first factor the quadratic expression. We need two numbers that multiply to -15 (the constant term) and add up to 2 (the coefficient of \( x \)). These numbers are 5 and -3. Thus, we can rewrite the equation as \( (x + 5)(x - 3) = 0 \). Setting each factor to zero gives us \( x + 5 = 0 \) or \( x - 3 = 0 \), leading to the solutions \( x = -5 \) and \( x = 3 \). For additional fun facts, did you know that quadratic equations have been studied for thousands of years? Ancient Babylonian mathematicians were solving these equations long before the advent of algebra as we know it today! They used geometric methods to tackle problems that we now handle with simple equations. If you ever face quadratic equations again, remember to check your factoring skills! A common mistake is not checking if both binomials equal zero or missing a negative sign. Always substitute your answers back into the original equation to verify they really work!

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