Use a system of linear equations to solve Exercises 73–84. How many ounces of a 15% alcohol solution must be mixed with 4 ounces of a 20% alcohol solution to make a 17% alcohol solution?
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7. Systems of Equations & Matrices
Two Variable Systems of Linear Equations
Problem 79
Textbook Question
Use a system of equations to solve each problem. Find an equation of the parabola y = ax2 + bx + c that passes through the points (2, 3), (-1, 0), and (-2, 2).
Verified step by step guidance1
Start by substituting each given point into the general form of the parabola equation \(y = ax^2 + bx + c\). For the point \((2, 3)\), substitute \(x = 2\) and \(y = 3\) to get the equation \$3 = a(2)^2 + b(2) + c$.
Next, substitute the point \((-1, 0)\) into the equation by setting \(x = -1\) and \(y = 0\), which gives \$0 = a(-1)^2 + b(-1) + c$.
Then, substitute the point \((-2, 2)\) by setting \(x = -2\) and \(y = 2\), resulting in \$2 = a(-2)^2 + b(-2) + c$.
Now, simplify each equation to form a system of three linear equations in terms of \(a\), \(b\), and \(c\). This system will look like: \$4a + 2b + c = 3\(, \)a - b + c = 0\(, and \)4a - 2b + c = 2$.
Solve this system of equations using either substitution, elimination, or matrix methods to find the values of \(a\), \(b\), and \(c\). These values will give you the specific equation of the parabola.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
System of Equations
A system of equations consists of multiple equations with multiple variables that are solved together. In this problem, each point provides an equation when substituted into y = ax^2 + bx + c, creating a system to find a, b, and c.
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Quadratic Function Form
The quadratic function y = ax^2 + bx + c represents a parabola, where a, b, and c are constants. Understanding this form allows you to set up equations by plugging in x and y values from given points.
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Vertex Form
Substitution of Points into Equations
Substituting each point's coordinates into the quadratic equation generates specific equations. This step translates geometric information into algebraic form, enabling the creation of a solvable system.
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