Chapter 1: Problem 21
For Problems \(21-30\), fill in the blanks with a pair of numbers that has the indicated product and the indicated sum. For example, \(8 \cdot 5=40\) and \(8+5=13\). \(\cdot \quad=24\) and \(\quad+\quad=11\)
Short Answer
Expert verified
The numbers are 3 and 8.
Step by step solution
01
Understand the Problem
We need to find two numbers whose product is 24 and whose sum is 11. Let's call these numbers \( x \) and \( y \). This gives us two equations: \( x \cdot y = 24 \) and \( x + y = 11 \).
02
Setup Equations
We have two equations: \( x \cdot y = 24 \) and \( x + y = 11 \). Let's use these equations to find the values of \( x \) and \( y \).
03
Solve for One Variable
From the second equation \( x + y = 11 \), express \( y \) in terms of \( x \): \( y = 11 - x \).
04
Substitute and Solve
Substitute \( y = 11 - x \) into the first equation \( x \cdot y = 24 \):\[x(11 - x) = 24\]Expand and rearrange the equation:\[11x - x^2 = 24 \Rightarrow x^2 - 11x + 24 = 0\]
05
Factor the Quadratic Equation
Now, factor \( x^2 - 11x + 24 = 0 \). Look for two numbers that multiply to 24 and add to -11. These numbers are -3 and -8.So, the equation factors to:\[(x - 3)(x - 8) = 0\]
06
Solve for x
Set each factor to zero: \(x - 3 = 0\) or \(x - 8 = 0\),Solving these gives \(x = 3\) or \( x = 8\).
07
Find Corresponding y Values
Substitute back to find \( y \). For \( x = 3 \), \( y = 11 - 3 = 8 \). For \( x = 8 \), \( y = 11 - 8 = 3 \).
08
Verify the Solution
Check both pairs (3, 8) and (8, 3): * Product: \(3 \cdot 8 = 24\) * Sum: \(3 + 8 = 11\)Both pairs satisfy the original conditions.
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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 where the highest exponent of the variable is two. They take the form: \[ ax^2 + bx + c = 0 \]where \( a \), \( b \), and \( c \) are constants. The solutions to these equations are the values of \( x \) that make the equation true. Understanding how to solve quadratic equations is crucial in algebra.
Generally, quadratic equations can be solved using:
Generally, quadratic equations can be solved using:
- Factoring
- Completing the square
- Using the quadratic formula: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]
Factoring
Factoring is a technique used to break down expressions into simpler "factors" that multiply together to give the original expression, similar to finding the ingredients that make a dish. In the context of solving quadratic equations, factoring involves rewriting the quadratic as a product of two binomials. This approach is handy when the quadratic equation is factorable, which means it can be expressed as:\[(x - p)(x - q) = 0\]where \( p \) and \( q \) are the roots (solutions) of the equation.
For the equation \( x^2 - 11x + 24 = 0 \), we factored it into:\[(x - 3)(x - 8) = 0\]This choice of binomial factors was possible because 3 and 8 multiply to 24 and add up to 11 (the linear coefficient).
For the equation \( x^2 - 11x + 24 = 0 \), we factored it into:\[(x - 3)(x - 8) = 0\]This choice of binomial factors was possible because 3 and 8 multiply to 24 and add up to 11 (the linear coefficient).
- The first step is to check whether simple factorization is feasible.
- Identify the numbers that multiply to the constant term (in this case, 24).
- Make sure these numbers also add up to the middle coefficient (here, -11).
System of Equations
A system of equations consists of multiple equations that are solved together since they share variables. In the original problem, we identified the system:
To solve a system:
- \( x \cdot y = 24 \)
- \( x + y = 11 \)
To solve a system:
- Express one variable in terms of the other. In this problem, we used \( y = 11 - x \).
- Substitute this expression back into the other equation. This reduces the system to a single equation with one variable.
- Solve the resulting equation using appropriate algebraic methods—here, that meant solving the quadratic form.