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Where’s the Function?

This question was another question from the January 2013 C3 paper that I remember almost foxing some of my students of the time:

image

It’s a strange question in that it asks for ff(-3) but, unusually, doesn’t define the function algebraically. I remember the day of the exam three of them discussing the paper with me after sitting it saying “it was a well weird function question, it just showed you the graph.” That day they had worked it out, but I feel that the time taken had contributed to at least two of them running out of time later in the paper.

So on Friday when a couple of learners asked for my help and I saw they were working on this question I didn’t even need to ask what their issue was. I started by reminding them that the graph was the function and that they didn’t need it algebraically to get an answer as there was enough information on the graph to answer it. We discussed this and they realised that the y coordinate is what comes out of the function when you put the x value in.

It’s a nice question, it highlights a possible blind spot that I need to address and shows us one of the pitfalls of an over reliance on past papers in revision. Past papers are a key part of revision, don’t get me wrong. But they shouldn’t be the only part of it, as otherwise a curveball question like this, one that asks something in a slightly different way, can really throw you off.

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  1. April 12, 2015 at 6:26 pm

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