Chapter 4: Problem 78
Factor. \(-2 x^{2}+13 x-20\)
Short Answer
Expert verified
The factorized form is
\((-2x + 5)(x - 4)\).
Step by step solution
01
Identify the Coefficients
First, identify the coefficients of the quadratic expression \(-2x^2 + 13x - 20\). These are: \(a = -2\), \(b = 13\), and \(c = -20\).
02
Determine Product and Sum
We need to find two numbers that multiply to \(a \times c = -2 \times -20 = 40\) and add up to \(b=13\).
03
Find Suitable Numbers
The numbers that multiply to \(40\) and add up to \(13\) are \(5\) and \(8\) because \(5 \times 8 = 40\) and \(5 + 8 = 13\).
04
Rewrite the Middle Term
Rewrite the middle term using the numbers found: \(-2x^2 + 5x + 8x - 20\).
05
Factor by Grouping
Group terms to help factorize: \((-2x^2 + 5x) + (8x - 20)\). Factor each group: \(x(-2x + 5) + 4(2x - 5)\).
06
Final Factorization
Notice that the expression from Step 5 is incorrect. Correct the binomials and complete the factorization: \(-1(x - 4)(2x - 5)\), where the expression should actually be grouped correctly respecting the signs and common factors.Thus the correct factorization is: \((-2x + 5)(x - 4)\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Coefficients
In the world of quadratic expressions, coefficients play a pivotal role. A quadratic expression typically takes the form of \(ax^2 + bx + c\), where \(a\), \(b\), and \(c\) are the quadratic coefficients. Each coefficient serves a specific purpose.
- \(a\) is the coefficient of \(x^2\). It can make the parabola open upwards or downwards.
- \(b\) is the coefficient of \(x\), it helps in determining the position and shape of the parabola.
- \(c\) is the constant term that affects the vertical position of the parabola.
Polynomial Factorization
Polynomial factorization involves breaking down a polynomial into simpler multiplicative components that can be multiplied together to get the original polynomial. Think of it like turning a complex whole into understandable parts.
- The goal is to express a polynomial as a product of its factors.
- Each factor is often a simpler polynomial or a constant.
Factoring by Grouping
Factoring by grouping is an efficient technique used when a polynomial can be divided into groups that can be easily factored separately.
- Start by breaking the polynomial into smaller groups which make factoring obvious.
- Factor each group individually.