Chapter 6: Problem 100
In the following exercises, factor completely using trial and error. $$ 5 x^{2}-17 x+6 $$
Short Answer
Expert verified
(5x - 2)(x - 3)
Step by step solution
01
- Identify the equation
The given quadratic equation is \[5x^2 - 17x + 6\].
02
- Find two numbers that multiply to ac
The coefficient of \(x^2\) is 5 (a=5), and the constant term is 6 (c=6). Multiply a and c: \[5 \times 6 = 30\]. Find two numbers that multiply to 30 and add up to the middle term's coefficient, -17.
03
- Identify the pair
The pair of numbers that multiply to 30 and add to -17 is -15 and -2, because \[-15 \times -2 = 30\] and \[-15 + -2 = -17\].
04
- Rewrite the middle term
Rewrite the quadratic expression using -15 and -2: \[5x^2 - 15x - 2x + 6\].
05
- Factor by grouping
Group the terms into two pairs and factor out the common factors: \[5x(x - 3) - 2(x - 3)\].
06
- Factor out the common binomial
Observe that \(x - 3\) is common in both terms: \[(5x - 2)(x - 3)\].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
quadratic equations
A quadratic equation is a polynomial equation of degree 2. This means that the highest exponent of the variable (usually x) is 2. The general form of a quadratic equation is given as: \[ax^2 + bx + c = 0\], where:
- \(a\), \(b\), and \(c\) are constants
- \(a eq 0\)
factoring by grouping
Factoring by grouping is a method used to factor polynomials with four or more terms. The goal is to rearrange and group terms that have a common factor. For example, given \[5x^2 - 15x - 2x + 6\], you can group the terms as follows: \[(5x^2 - 15x) + (-2x + 6)\].
Next, factor out the greatest common factor (GCF) from each group:
Next, factor out the greatest common factor (GCF) from each group:
- In the first group \(5x^2 - 15x\), the GCF is 5x: \[5x(x - 3)\]
- In the second group \(-2x + 6\), the GCF is -2: \[-2(x - 3)\]
trial and error method
The trial and error method for factoring quadratics involves finding two numbers that satisfy specific conditions. In this example, given \[5x^2 - 17x + 6\], we look for two numbers that multiply to \(5 \times 6 = 30\) (product of the coefficient of \(x^2\) and the constant term)
and add to -17 (the coefficient of the middle term). After testing possible pairs, we find that -15 and -2 work because:
and add to -17 (the coefficient of the middle term). After testing possible pairs, we find that -15 and -2 work because:
- \(-15 \times -2 = 30\)
- \(-15 + -2 = -17\)
polynomial factoring
Polynomial factoring is the process of breaking down a polynomial into simpler components. These factors, when multiplied together, give back the original polynomial.
In our example, factoring \(5x^2 - 17x + 6\) completely resulted in \[(5x - 2)(x - 3)\], which are both simpler polynomials. Factoring polynomials is a foundational skill in algebra and finding zeros of polynomials. It often involves techniques such as:
In our example, factoring \(5x^2 - 17x + 6\) completely resulted in \[(5x - 2)(x - 3)\], which are both simpler polynomials. Factoring polynomials is a foundational skill in algebra and finding zeros of polynomials. It often involves techniques such as:
- Factoring by grouping
- Trial and error method
- Using special products like difference of squares