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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 15

In Exercises 1–26, graph each inequality. x2+y2>25

Guida verificata passo dopo passo
1
Recognize that the inequality x2 + y2 > 25 represents all points (x, y) whose distance from the origin is greater than 5, since 25 = 5^2.
Start by graphing the boundary circle defined by the equation x2 + y2 = 25. This circle has center at (0,0) and radius 5.
Since the inequality is strict (>), the points on the circle itself are not included, so represent the boundary with a dashed circle to indicate that points on the circle are excluded.
Determine which side of the circle to shade by testing a point not on the circle, such as the origin (0,0). Substitute into the inequality: 0^2 + 0^2 = 0, which is not greater than 25, so the origin is not part of the solution.
Shade the region outside the circle because the inequality x2 + y2 > 25 means all points whose distance from the origin is greater than 5.

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Graphing Inequalities in Two Variables

Graphing inequalities involves shading regions of the coordinate plane that satisfy the inequality. For inequalities with two variables, the boundary is found by replacing the inequality with an equation, and then the solution region is determined by testing points to see which side satisfies the inequality.
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Equations with Two Variables

Equation of a Circle

The equation x² + y² = r² represents a circle centered at the origin with radius r. Understanding this helps identify the boundary curve for inequalities involving x² + y², such as x² + y² > 25, where the radius is 5.
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Circles in Standard Form

Strict vs. Non-Strict Inequalities and Boundary Lines

A strict inequality (>, <) means the boundary line or curve is not included in the solution set, so it is drawn as a dashed line or curve. For x² + y² > 25, points on the circle are excluded, and the solution is the region outside the circle.
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Parallel & Perpendicular Lines