Chapter 11: Problem 17
Solve each system by using the substitution method. \(\left(\begin{array}{l}a=4 b+13 \\ 3 a+6 b=-33\end{array}\right)\)
Short Answer
Expert verified
The solution is \( a = -3 \) and \( b = -4 \).
Step by step solution
01
Solve the First Equation for 'a'
The first equation is given as \( a = 4b + 13 \). This is already solved for \( a \), so we can use this expression directly in the next step.
02
Substitute 'a' in the Second Equation
Substitute the expression we found for \( a \) into the second equation. Replace \( a \) in \( 3a + 6b = -33 \) with \( 4b + 13 \). This gives:\[3(4b + 13) + 6b = -33\]
03
Simplify the Equation
Expand and simplify the equation from Step 2:\[3(4b + 13) + 6b = 12b + 39 + 6b = -33\]Combine like terms:\[12b + 6b + 39 = -33\]\[18b + 39 = -33\]
04
Solve for 'b'
Subtract 39 from both sides of the equation:\[18b = -33 - 39\]\[18b = -72\]Divide by 18:\[b = -4\]
05
Solve for 'a' Using 'b'
Now that we have \( b = -4 \), substitute this back into the first equation \( a = 4b + 13 \):\[a = 4(-4) + 13\]\[a = -16 + 13\]\[a = -3\]
06
Verify the Solution
Substitute \( a = -3 \) and \( b = -4 \) back into both original equations to verify:- For the first equation: \( -3 = 4(-4) + 13 \) simplifies to \( -3 = -16 + 13 \), which holds true.- For the second equation: \( 3(-3) + 6(-4) = -33 \) simplifies to \( -9 - 24 = -33 \), which holds true. Thus, our solution is verified.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
The System of Equations
In algebra, a system of equations consists of two or more equations with the same set of variables. By solving a system of equations, we are finding the values of the variables that satisfy all the equations simultaneously. In the given exercise, our system of equations is:
- \( a = 4b + 13 \)
- \( 3a + 6b = -33 \)
Understanding Linear Equations
Linear equations are the foundation of solving systems by the substitution method. Each equation in our system can be written in the general form \( ax + by = c \), where \( a \), \( b \), and \( c \) are constants, and \( x \) and \( y \) are variables.
In the exercise, the equations can be seen as relationships between \( a \) and \( b \). They describe planes in a two-dimensional space. When solving linear systems, our aim is to find values for \( a \) and \( b \) that satisfy both linear relationships at the same time.
But unlike graphical methods that require plotting, solving algebraically using substitution provides a precise solution without needing a graph.
In the exercise, the equations can be seen as relationships between \( a \) and \( b \). They describe planes in a two-dimensional space. When solving linear systems, our aim is to find values for \( a \) and \( b \) that satisfy both linear relationships at the same time.
But unlike graphical methods that require plotting, solving algebraically using substitution provides a precise solution without needing a graph.
- Equation 1, \( a = 4b + 13 \), easily isolates \( a \) in terms of \( b \).
- Equation 2, \( 3a + 6b = -33 \), uses these variables in combination.
Algebra Problem Solving with Substitution Method
The substitution method is a straightforward technique for solving systems of equations. Here's how it works step by step:
- **Isolate**: First, pick one equation and isolate one variable. In our exercise, the first equation is already solved for \( a \) (\( a = 4b + 13 \)).
- **Substitute**: Substitute this expression for the isolated variable into the other equation. Here, we substitute \( 4b + 13 \) for \( a \) in the second equation: \( 3(4b + 13) + 6b = -33 \)
- **Solve**: Solve the resulting equation for the remaining variable. Simplifying gives \( b = -4 \).
- **Back-substitute**: Finally, substitute back to find the other variable. Use \( b = -4 \) in \( a = 4b + 13 \) to find \( a = -3 \).