Chapter 0: Problem 15
\(13-20\) . Factor the trinomial. $$ x^{2}+2 x-15 $$
Short Answer
Expert verified
The trinomial \(x^2 + 2x - 15\) factors to \((x - 3)(x + 5)\).
Step by step solution
01
Understand the Problem
We need to factor the trinomial \(x^2 + 2x - 15\). This involves writing it as a product of two binomials.
02
Identify the Pattern
The trinomial is in the form \(ax^2 + bx + c\) where \(a = 1\), \(b = 2\), and \(c = -15\). Since \(a = 1\), we need to find two integers that multiply to \(c = -15\) and add to \(b = 2\).
03
Find Pairs of Numbers
Identify pairs of integers whose product is \(-15\). These pairs include \((-1, 15), (1, -15), (-3, 5), (3, -5)\).
04
Select the Correct Pair
Find the pair that adds up to \(b = 2\). The pair \((-3, 5)\) satisfies this condition as \(-3 + 5 = 2\).
05
Write the Factored Form
Use the pair \((-3, 5)\) to write the factors. The trinomial factors into \((x - 3)(x + 5)\).
06
Double-Check the Factorization
Multiply \((x - 3)(x + 5)\) to ensure it expands back to \(x^2 + 2x - 15\) which confirms our factorization.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Equations
Quadratic equations are a type of polynomial equation that have the highest degree of two, meaning the variable (typically represented as \(x\)) is squared. They typically appear in the form \(ax^2 + bx + c = 0\), where \(a\), \(b\), and \(c\) are constants. These equations can graphically be represented by parabolas.
- When solving these equations, the goal can often be to find the values of \(x\) that satisfy the equation (the roots).
- A key characteristic of quadratic equations is that each equation can have up to two real roots.
Binomial Products
Binomial products result when two binomial expressions are multiplied together. A binomial is a polynomial with two terms, such as \((x - 3)\) or \((x + 5)\). Multiplying two binomials, say \((a + b)(c + d)\), involves using the distributive property or the FOIL method:
- First: Multiply the first terms of each binomial.
- Outer: Multiply the outer terms of the bins.
- Inner: Multiply the inner terms.
- Last: Multiply the last terms of each binomial.
- First: \(x \cdot x = x^2\)
- Outer: \(x \cdot 5 = 5x\)
- Inner: \(-3 \cdot x = -3x\)
- Last: \(-3 \cdot 5 = -15\)
Integer Factorization
Integer factorization involves breaking down an integer into a product of smaller integers, which are often prime numbers. When applied to trinomials in algebra, integer factorization refers to finding integers that fulfill certain conditions required to factor a quadratic equation.
For instance, to factor \(x^2 + 2x - 15\), we needed to identify two numbers that multiply to \(-15\) and also add up to \(2\). This uses the concept of integer factorization:
For instance, to factor \(x^2 + 2x - 15\), we needed to identify two numbers that multiply to \(-15\) and also add up to \(2\). This uses the concept of integer factorization:
- Look for pairs of numbers that multiply to the constant term (here, \(-15\)).
- Check which of these pairs, when added together, result in the middle coefficient (here, \(2\)).