Domain, Range, and Translating Functions
Date: 06/29/2004 at 22:10:38 From: Scarlet Subject: Functions, domain, range, absolute value etc. - Algebra I'm doing my summer review packet for my Algebra 2 With Analysis class (for next school year), but I'm stuck on a function question. 1. Given the graph of y = f(x), domain [-4,3], range [-2,3], I am then asked to sketch four other functions, such as y = |f(x)| and y = f(x - 2) and find the domain and range of each. I've sort of figured out that y = f(x - 2) should move the graph to the right by 2 units, and y = (1/2)f(x) should make the graph thinner (I don't know how to describe it). But how do I determine the domain and range of each? Oh, the original graph of f(x) is sort of like a V--it's two line segments, but they don't have the same steepness or slope.
Date: 06/29/2004 at 23:25:05 From: Doctor Peterson Subject: Re: Functions, domain, range, absolute value etc. - Algebra Hi, Scarlet. Here are some pages on similar problems: Graph with f(x) http://mathforum.org/library/drmath/view/54509.html Translating Functions http://mathforum.org/library/drmath/view/54472.html Graphing Absolute Values http://mathforum.org/library/drmath/view/60968.html Graphing the Absolute Value/Square Root of a Function http://mathforum.org/library/drmath/view/61112.html Those show how to graph a transformed function. Once you've done that, you can use the features you graphed to determine the domain and range. Based on your description, let's suppose the original graph looks like this: | * + \ | \ + \ | \ + * \ | / --+--+--\--+--+--+--/--+-- \ | / \ + / \ / * + | The domain is the "shadow" under it; that is, it's the set of values on the x-axis for which the function is defined. Visually, | * + :\ | : \ + : \ | : \ + * : \ | /: --+--+--\--+--+--+--/--+-- \ | / \ + / \ / * + | +====================+ -4 domain 3 The range is the "shadow" on the y-axis, that is, the set of values of y that the function ever takes. Look for the lowest and highest values, as well as any possible gaps: | *. . . . . .+ + 3 \ | | \ + | \ | | \ + * | \ | / |range --+--+--\--+--+--+--/--+-- | \ | / | \ + / | \ / | *.+ +-2 | Now, if you transform a function by shifting it right, the domain is shifted right. If you transform it by shifting it up, the range is shifted up. For other cases, you can figure out how the domain and/or range are affected by thinking about how the graph is changed. In some cases you have to do some extra thinking, such as determining exactly where certain points on the graph are transformed to. Here are some pages on domain and range: Range and Domain of a Graph http://mathforum.org/library/drmath/view/54576.html Domain and Range http://mathforum.org/library/drmath/view/54551.html Interval Notation http://mathforum.org/library/drmath/view/52929.html If you have any further questions, feel free to write back. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/
Date: 07/01/2004 at 15:35:06 From: Scarlet Subject: Thank you (Functions, domain, range, absolute value etc. - Algebra ) Dear Dr. Peterson, THANKS A LOT for your help! Your explanations have been very useful and easy to understand--not just for me but for some of my friends who had the same or similar questions as well! It was especially helpful as many of my teachers are not available for help during the summer. THANKS AGAIN for all your help!! - Scarlet
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