How to Graph for Algebra 2

Algebra I introduces graphing and covers straight lines and parabolas. Algebra II introduces more-complex aspects of the graphing process, such as asymptotes -- a line a graph approaches closer and closer but never touches. Other aspects of graphing covered in Algebra II is the mathematical way to move the graph around by modifying the formula and how to shrink and stretch the graph to fit a page.

Instructions

    • 1

      Find the asymptotes and represent them with a dashed line. Choose graphing points to include several near the asymptote and graph in the normal way. For example, when graphing the function y = 1/(x -3), there is an asymptote at x = 3, because y is undefined when x = 3. Choosing points near the asymptote we find 1/(3.01 - 3) = 100 and 1/(2.99 - 3) = -100. The graph goes up along the right side of the asymptote and down along the left side of the asymptote.

    • 2

      Move the graph around the page. Modifying the x in the equation moves the graph left and right. So adding 2 to the x in an equation moves it two places. Y = 1/((X + 2) - 3 = 1/(X -1). The graph of y = 1/(X -1) looks exactly like the graph of Y = 1/(X - 3) except it is shifted two units to the left. Similarly, adding 2 to the y part gives (y + 2) = 1/(x - 3) or y = 1/(x - 3) - 2 = (7 - 2x)/3 - 5 which is the same graph shifted two units down. Subtracting a distance from the Y shifts the entire graph up on the page.

    • 3

      Scale the graph to fit the page. The general formula for vertical stretching and shrinking a formula y = f(x) is y = af(x) when a > 0. Stretching takes place where a > 1; shrinking takes place when a < 1. So the graph of y = 1/(x-3) is doubled in the vertical direction if you graph y = 2/(X-3) instead, and shrunk by half in the vertical direction if you graph y = 0.5/(x - 3). Horizontal scaling of y = f(x) is accomplished by y = f(bx). To stretch y = 1/(x-3) horizontally use y = 1/(2X - 3); to shrink it use y = 1/(0.5x - 3).

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