ckfeister
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a) Find the area between the y-axis, and the curves y = x2 and y = 2 + √2√x, given that the curves intersect at (2,4)

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Here is my workings out but it says the answer is 4 sq. units... what have I done wrong along the way?
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Muttley79
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(Original post by ckfeister)
a) Find the area between the y-axis, and the curves y = x2 and y = 2 + √2√x, given that the curves intersect at (2,4)

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Views: 137
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Here is my workings out but it says the answer is 4 sq. units... what have I done wrong along the way?
Check your second integration - the integral of 2 is not 2 and the second term is also incorrect.
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ckfeister
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(Original post by Muttley79)
Check your second integration - the integral of 2 is not 2 and the second term is also incorrect.
Its 2x and got 9 1/3 sq. unit now.... what am I doing wrong? The answer is 4.
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ckfeister
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(Original post by Muttley79)
Check your second integration - the integral of 2 is not 2 and the second term is also incorrect.
Ohh forgot to do the bottom part, I got 68/9 for second part, but got 44/9 sq.unit now (4.8888...) what else have I done wrong?
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Muttley79
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(Original post by ckfeister)
Ohh forgot to do the bottom part, I got 68/9 for second part, but got 44/9 sq.unit now (4.8888...) what else have I done wrong?
They want the area between the curcve and the Y AXIS ... what are you finding?
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Sir Cumference
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(Original post by ckfeister)
Ohh forgot to do the bottom part, I got 68/9 for second part, but got 44/9 sq.unit now (4.8888...) what else have I done wrong?
You should be getting 20/3 for your second integral.

Have another go and please post your working if you don't get it.
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ckfeister
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(Original post by Muttley79)
They want the area between the curcve and the Y AXIS ... what are you finding?
I got the integral wrong I forgot you add one power and divide by the new power. I'm using x = 2 x = 0 as the area finder.
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ckfeister
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(Original post by notnek)
You should be getting 20/3 for your second integral.

Have another go and please post your working if you don't get it.
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I can't see how I can improve from this... can you hint it out?
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Muttley79
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(Original post by ckfeister)
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I can't see how I can improve from this... can you hint it out?
Check what you are doing - I can't see that you are finding the right area - where are you dealing with the y-axis?
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ckfeister
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(Original post by Muttley79)
Check what you are doing - I can't see that you are finding the right area - where are you dealing with the y-axis?
(2,4) is the intersecting points, so I'm using 2,0, this is the area for area B (one thats wrong) I don't see how it 20/3 but somehow it is.
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Muttley79
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(Original post by ckfeister)
(2,4) is the intersecting points, so I'm using 2,0, this is the area for area B (one thats wrong) I don't see how it 20/3 but somehow it is.
The area should be integrated with respect to y shouldn't it...
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Sir Cumference
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(Original post by ckfeister)
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I can't see how I can improve from this... can you hint it out?
Your problem is with the integral of 2^\frac{1}{2}x^\frac{1}{2}

Remember that 2^\frac{1}{2} is just a number like 2 so hink about how you integrate 2x^\frac{1}{2} and do a similar thing here.
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Sir Cumference
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(Original post by ckfeister)
a) Find the area between the y-axis, and the curves y = x2 and y = 2 + √2√x, given that the curves intersect at (2,4)
I just noticed that the question includes the y-axis, as Muttley has pointed out.

Are you sure you posted the question correctly? It doesn't really make sense. The area between the two curves is 4 so I assumed that was the question.
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ckfeister
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(Original post by notnek)
I just noticed that the question includes the y-axis, as Muttley has pointed out.

Are you sure you posted the question correctly? It doesn't really make sense. The area between the two curves is 4 so I assumed that was the question.
I copied and pasted the entire question and yes it doesn't, cloudlearn are good at confusing me.
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ckfeister
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(Original post by Muttley79)
The area should be integrated with respect to y shouldn't it...
Not according to the question, its all y = (..)
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Muttley79
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(Original post by ckfeister)
Not according to the question, its all y = (..)
Irrelevant - what you are doing at the moment is finding the area between the curve and the x-axis.
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ckfeister
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(Original post by Muttley79)
Irrelevant - what you are doing is finding the area between the curve and the x-axis.
Do I flip the x formulas to y or..?
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Sir Cumference
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(Original post by Muttley79)
Irrelevant - what you are doing at the moment is finding the area between the curve and the x-axis.
The OP's method will work.




The questions asks for the area bounded by the two curves and the y-axis.
The OP is finding the area below the blue curve and subtracting the area below the black curve.
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Sir Cumference
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(Original post by ckfeister)
...
Ignore what I said before about the question being wrong - I had pictured it incorrectly. See my post above for a proper picture.

The question is fine.
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Muttley79
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(Original post by notnek)
The OP's method will work.




The questions asks for the area bounded by the two curves and the y-axis.
The OP is finding the area below the blue curve and subtracting the area below the black curve.
I don't think the OP really understands though - I would have drawn a sketch and explained why I was integrating wrt x.
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