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Ch. 5 - Systems of Equations and Inequalities
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Non è quello che usi tu?Cambia libro di testo
Capitolo 6, Problema 11

In Exercises 1–18, solve each system by the substitution method. {y2=x2−92y=x−3\(\begin{cases}\) y^2 = x^2 - 9 \\ 2y = x - 3 \(\end{cases}\)

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1
Start with the given system of equations: \(y^2 = x^2 - 9\) and \(2y = x - 3\).
From the second equation, solve for \(x\) in terms of \(y\): \(2y = x - 3\) implies \(x = 2y + 3\).
Substitute the expression for \(x\) from step 2 into the first equation: \(y^2 = (2y + 3)^2 - 9\).
Expand the right side: \((2y + 3)^2 = 4y^2 + 12y + 9\), so the equation becomes \(y^2 = 4y^2 + 12y + 9 - 9\).
Simplify and rearrange the equation to isolate terms and form a quadratic equation in \(y\): \(y^2 = 4y^2 + 12y\), then bring all terms to one side to solve for \(y\).

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Substitution Method

The substitution method involves solving one equation for one variable and then substituting that expression into the other equation. This reduces the system to a single equation with one variable, making it easier to solve. It is especially useful when one equation is already solved or easily solvable for one variable.
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Solving Quadratic Equations

Quadratic equations involve variables raised to the second power and can have two solutions. When substituting, the resulting equation may be quadratic, requiring methods like factoring, completing the square, or the quadratic formula to find solutions. Understanding how to solve quadratics is essential for finding all possible solutions.
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Checking Solutions in Systems

After finding potential solutions, it is important to verify them by substituting back into the original equations. This ensures that the solutions satisfy both equations, especially since squaring or other operations can introduce extraneous solutions. Checking helps confirm the accuracy and validity of the answers.
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