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- [Instructor] We're told this table defines function f.
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All right.
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For every x, they give us the corresponding f of x.
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According to the table, is f even, odd, or neither?
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So pause this video and see
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if you can figure that out on your own.
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All right, now let's work on this together.
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So let's just remind ourselves the definition
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of even and odd.
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One definition that we can think of is that f of x,
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if f of x is equal to f of negative x,
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then we're dealing with an even function.
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And if f of x is equal
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to the negative of f of negative x,
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or another way of saying that, if f of negative x.
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If f of negative x, instead of it being equal to f of x,
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it's equal to negative f of x.
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These last two are equivalent.
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Then in these situations,
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we are dealing with an odd function.
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And if neither of these are true,
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then we're dealing with neither.
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So what about what's going on over here?
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So let's see.
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F of negative seven is equal to negative one.
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What about f of the negative of negative seven?
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Well, that would be f of seven.
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And we see f of seven here is also equal to negative one.
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So at least in that case and that case,
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if we think of x as seven,
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f of x is equal to f of negative x.
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So it works for that.
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It also works for negative three and three.
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F of three is equal to f of negative three.
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They're both equal to two.
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And you can see and you can kind of visualize in your head
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that we have symmetry around the y-axis.
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And so this looks like an even function.
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So I will circle that in.
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Let's do another example.
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So here, once again, the table defines function f.
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It's a different function f.
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Is this function even, odd, or neither?
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So pause this video and try to think about it.
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All right, so let's just try a few examples.
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So here we have f of five is equal to two.
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F of five is equal to two.
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What is f of negative five?
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F of negative five.
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Not only is it not equal to two,
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it would have to be equal to two
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if this was an even function.
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And it would be equal to negative two
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if this was an odd function, but it's neither.
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So we very clearly see just looking at that data point
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that this can neither be even, nor odd.
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So I would say neither or neither right over here.
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Let's do one more example.
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Once again, the table defines function f.
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According to the table, is it even, odd, or neither?
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Pause the video again.
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Try to answer it.
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All right, so actually let's just start over here.
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So we have f of four is equal to negative eight.
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What is f of negative four?
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And the whole idea here is I wanna say,
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okay, if f of x is equal to something,
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what is f of negative x?
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Well, they luckily give us f of negative four.
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It is equal to eight.
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So it looks like it's not equal to f of x.
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It's equal to the negative of f of x.
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This is equal to the negative of f of four.
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So on that data point alone,
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at least that data point satisfies it being odd.
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It's equal to the negative of f of x.
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But now let's try the other points just to make sure.
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So f of one is equal to five.
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What is f of negative one?
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Well, it is equal to negative five.
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Once again, f of negative x is equal
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to the negative of f of x.
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So that checks out.
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And then f of zero,
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well, f of zero is of course equal to zero.
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But of course if you say
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what is the negative of f of,
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if you say what f of negative of zero,
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well, that's still f of zero.
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And then if you were to take the negative of zero,
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that's still zero.
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So you could view this.
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This is consistent still with being odd.
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This you could view as the negative of f of negative zero,
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which of course is still going to be zero.
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So this one is looking pretty good that it is odd.