# 9-1-4 - 1-4 Quadratic Functions and Their Graphs Sketching...

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Unformatted text preview: 1-4 Quadratic Functions and Their Graphs Sketching the graph of a parabola: f(x) = ax2 + bx + c 1. if a > 0, it opens up if a < 0, it opens down − b − b , f this is a key point! 2. plot vertex: 2a 2a 3. plot x-intercepts: solve f(x) = 0 to get them 4. plot y-intercept: f(0) = c, so y-intercept = c 5. plot more points on either side of the vertex as necessary to round out picture Example: f(x) = -x2 + 2x + 3 (a = -1, b = 2, c = 3) 1. a < 0 so 2. = = f() = , so 3. solve -x2 + 2x + 3 = 0: (-x + 3)(x + 1) = 0 x = 3, -1 4. c = 3, so 5. f(2) = 3 opens down 1-4 vertex: (1,4) x-intercepts: (3, 0), (-1, 0) y-intercept: (0, 3) additional point: (2,3) p. 1 ...
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## This note was uploaded on 12/11/2011 for the course MATH 1324 taught by Professor Staff during the Spring '11 term at Austin Community College.

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