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IS THIS GRAPH RIGHT? (Taking into account domain )

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Reply 20
Avatar for Jane122
Jane122
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Original post by BobBobson
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.


I know what you mean but the way I drew the graph it's passing through 4 and not touching 5:frown:
Original post by Jane122
I know what you mean but the way I drew the graph it's passing through 4 and not touching 5:frown:


Yeah that's wrong as well, because now your function isn't even valid. For a function to be a valid, each x value within the domain can only be paired with either 0 or 1 y value. For x=4, it has infinite y values, since the line is going straight down.
Reply 22
Avatar for Jane122
Jane122
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Original post by BobBobson
Yeah that's wrong as well, because now your function isn't even valid. For a function to be a valid, each x value within the domain can only be paired with either 0 or 1 y value. For x=4, it has infinite y values, since the line is going straight down.


But it's not a 1 to 1 function..
Original post by Jane122
But it's not a 1 to 1 function..


It doesn't have to be. If an x value has more than one y value, it's not a valid function.
Reply 24
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Jane122
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Original post by BobBobson
It doesn't have to be. If an x value has more than one y value, it's not a valid function.


IMG_2922.jpg Like this?!!! Even if it goes through 4 isn't it still less than equal to 4 since it's not touching 5 and so on
Original post by Jane122
IMG_2922.jpg Like this?!!! Even if it goes through 4 isn't it still less than equal to 4 since it's not touching 5 and so on


No, because if it goes through 4, it means it's touching 4.1 or 4.0000000001, which is greater than 4 and not <= 4. It must stop exactly dead at 4
Reply 26
Avatar for Jane122
Jane122
OP
2
Original post by BobBobson
No, because if it goes through 4, it means it's touching 4.1 or 4.0000000001, which is greater than 4 and not <= 4. It must stop exactly dead at 4


OHHHHH!!!!! OMG I finally understand LOL thank you so much!!!! I could kiss you.this stumped me for 1hr
You're welcome
Always try to be accurate, it's good practice.

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