IS THIS GRAPH RIGHT? (Taking into account domain ) Watch

Jane122
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Hi check my graph please.Name:  IMG_2900.jpg
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Jane122
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SeanFM Maths 123 gdunne42
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Kevin De Bruyne
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Almost, I would be persnickety and say that the graph is not defined for x>4 or x<0 so there should be no lines there.
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the bear
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the curve should begin at ( 2, 4 ) ... this means it will be higher than the end of the straight line, which ends at ( 2, 2 )
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Jane122
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(Original post by SeanFM)
Almost, I would be persnickety and say that the graph is not defined for x>4 or x<0 so there should be no lines there.

I'm confused 😅
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Kevin De Bruyne
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(Original post by Jane122)
I'm confused 😅
Well, what is f(-1)? How about f(5)? The answer is that they are not defined by the function f(x) so there should not be any y values for x values outside of the specified range. Your graph suggests that f(-1) = -1 and f(5) = 4*5 - 25.

And as the bear said.. I hadn't noticed.. your line should finish below the curve, if you see his post you'll understand why.
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Jane122
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(Original post by the bear)
the curve should begin at ( 2, 4 ) ... this means it will be higher than the end of the straight line, which ends at ( 2, 2 )
Like this ?Name:  IMG_2901.jpg
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Jane122
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(Original post by SeanFM)
Well, what is f(-1)? How about f(5)? The answer is that they are not defined by the function f(x) so there should not be any y values for x values outside of the specified range. Your graph suggests that f(-1) = -1 and f(5) = 4*5 - 25.

And as the bear said.. I hadn't noticed.. your line should finish below the curve, if you see his post you'll understand why.
F(1) is -5 and f(5) is also -5
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Kevin De Bruyne
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(Original post by Jane122)
F(1) is -5 and f(5) is also -5
They are not. Y values for this f(x) only exist between x=0 and x = 4. -5 and 5 are outside of this range so they have no corresponding y values.
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Jane122
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(Original post by SeanFM)
They are not. Y values for this f(x) only exist between x=0 and x = 4. -5 and 5 are outside of this range so they have no corresponding y values.
So the graph should end at 4? How am I supposed to know that?
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fatima359
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I'm not the only one whose looking at the graph and thinking WTF? 😁😁😁 Am I??


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Kevin De Bruyne
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(Original post by Jane122)
So the graph should end at 4? How am I supposed to know that?
From the definition of the function.
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fatima359
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I'm not the only one whose looking at this graph and thinking WTF am I?? 😁😁


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Ua3142
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(Original post by Jane122)
Hi check my graph please.Name:  IMG_2900.jpg
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Size:  304.5 KB
ahh flashbacks! burn it! BURN IT!!!111ERE
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Jane122
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(Original post by SeanFM)
From the definition of the function.
Ok I am really really stuck.. I don't know why the graph stops dead at 4? Like if you draw beyond but that are the values not less than 4 still?
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BobBobson
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(Original post by Jane122)
So the graph should end at 4? How am I supposed to know that?
Since there is no function defined for any x after 4 or before 0, so no graph can be plotted. Also the endpoint for 4x-x^2 should be coloured in since it's not a strict inequality
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Jane122
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(Original post by BobBobson)
Since there is no function defined for any x after 4 or before 0, so no graph can be plotted. Also the endpoint for 4x-x^2 should be coloured in since it's not a strict inequality
Name:  IMG_2921.jpg
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Size:  497.4 KB But the 4x-x^2 graph is going through 4???
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Kevin De Bruyne
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(Original post by Jane122)
Ok I am really really stuck.. I don't know why the graph stops dead at 4? Like if you draw beyond but that are the values not less than 4 still?
If you were in a sweet factory and there was a sign that said 'red sweets go into box 1 and blue sweets go into box 2' then where would green sweets go? Who knows. Green is not red or blue, so who can say where it goes? No one can. The same way this function tells you where values between 0 and 4 go but not for anything outside those values.
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Jane122
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(Original post by SeanFM)
If you were in a sweet factory and there was a sign that said 'red sweets go into box 1 and blue sweets go into box 2' then where would green sweets go? Who knows. Green is not red or blue, so who can say where it goes? No one can. The same way this function tells you where values between 0 and 4 go but not for anything outside those values.

I see what you mean like where would 5,6,7 etc go. But the way I drew the graph makes it look like it passes through 4
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BobBobson
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(Original post by Jane122)
Name:  IMG_2921.jpg
Views: 136
Size:  497.4 KB But the 4x-x^2 graph is going through 4???
4x-x^2 does go through 4 normally, however in your OP, you said the domain for it is 2<= x <= 4, so your x co-ordinates should stop dead at 4. Any number past 4 isn't in the domain of 4x-x^2, and thus shouldn't be plotted.
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