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Ch. 7 - Conic Sections
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514당신이 사용하는 게 아니라요?교과서 변경
8장, 문제 45

Convert each equation to standard form by completing the square on x or y. Then find the vertex, focus, and directrix of the parabola. Finally, graph the parabola. y2 - 2y + 12x - 35 = 0

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Start by rewriting the given equation: \(y^2 - 2y + 12x - 35 = 0\). Group the \(y\) terms together and move the \(x\) term and constant to the other side: \(y^2 - 2y = -12x + 35\).
Complete the square for the \(y\) terms. Take half of the coefficient of \(y\), which is \(-2\), divide by 2 to get \(-1\), then square it to get \(1\). Add \(1\) to both sides to maintain equality: \(y^2 - 2y + 1 = -12x + 35 + 1\).
Rewrite the left side as a perfect square: \((y - 1)^2 = -12x + 36\). Then isolate \(x\) by moving terms: \((y - 1)^2 = -12x + 36\) becomes \((y - 1)^2 = -12(x - 3)\).
Identify the vertex from the equation in standard form \((y - k)^2 = 4p(x - h)\), where the vertex is at \((h, k)\). Here, the vertex is at \((3, 1)\).
Determine the value of \(p\) by comparing \(-12\) to \$4p\(, so \(4p = -12\) which gives \)p = -3\(. Use \)p\( to find the focus at \)(h + p, k)\( and the directrix as the vertical line \)x = h - p$.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Completing the Square

Completing the square is a method used to rewrite quadratic expressions in the form (x - h)^2 or (y - k)^2 by adding and subtracting terms. This technique helps convert equations into standard form, making it easier to identify key features like the vertex of a parabola.
추천 영상:
06:24
Solving Quadratic Equations by Completing the Square

Standard Form of a Parabola

The standard form of a parabola's equation reveals its geometric properties clearly. For parabolas opening horizontally or vertically, the equation is written as (y - k)^2 = 4p(x - h) or (x - h)^2 = 4p(y - k), where (h, k) is the vertex and p relates to the distance between the vertex and the focus.
추천 영상:
5:33
Parabolas as Conic Sections

Vertex, Focus, and Directrix of a Parabola

The vertex is the parabola's turning point, the focus is a fixed point inside the parabola used to define it, and the directrix is a line perpendicular to the axis of symmetry. Knowing these helps in graphing the parabola and understanding its shape and orientation.
추천 영상:
7:18
Horizontal Parabolas Example 1