case 1

1
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When we get to those values of x what's
gonna be true about the sum?

2
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How about Mr. Torelli, what about these
negative function values in this

3
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interval of x Sabrina said the negative
values, what's that gonna

4
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do to the sum? The sum won't be as high.
What do you mean won't be as high?

5
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I think I know what you mean but be
more specific. You know how the line is

6
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going down with the points with the positive.
Ok with the sum it will still

7
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be in the positives, what would keep it
still in the positives? It was more

8
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positive than there is negative. Ok
good and this can be your ruler

9
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measurements. From some of these values
of x there's that much negative.

10
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But there's that much positive so it's
pulling it down but not yet to the

11
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point where the actual function value of
the sum is negative, ok so good.

12
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Alright so we said it starts to decrease,
I think we're still decreasing

13
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when is it going to cross the x axis?
Does it ever cross the x axis? Why not?

14
00:01:18-->00:01:24
What would it take for these two functuons,
for their sum to have a y value of 0.

15
00:01:25-->00:01:31
Or go beyond the x axis. Sabrina? Equal
amounts of positive or negative. Equal

16
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amounts of positive and negative and so did
that ever happen? Does that ever happen?

17
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No so you all agree. Riase our hand if your
graphs do not go back through the x axis

18
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anytime after here, so virually everyone.
So at least you agree on that.

19
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So we're decreasing but we never actually get
into those negatives ok well if we're

20
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decreasing and we never get into those negatives
that means we must start increasing

21
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again somewhere, because if we are on a decrease
right now, Mr Torilli just told us

22
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I should say so we should eventually go
negative unless my functions that do something

23
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that will make me think otherwise