# c4 integrating ln(x+2) by partsWatch

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Thread starter 6 years ago
#1
integrate ln(x+2) by parts
my working: u=lnx+2 du/dx =1/x+2, dv/dx=1 v=1 woops meant x
this makes
xln(x+2)-integral of x/x+2
i got xln(x+2)-x+0.25x2+c

however in the mark scheme it says this

is my answer the same? and if it is would i be awared the full marks
0
6 years ago
#2
(Original post by printergirl)
integrate ln(x+2) by parts
my working: u=lnx+2 du/dx =1/x+2, dv/dx=1 v=1
this makes
xln(x+2)-integral of x/x+2
i got xln(x+2)-x+0.25x2+c

however in the mark scheme it says this

is my answer the same? and if it is would i be awared the full marks
"dv/dx=1 v=1"

This is wrong. If DV/DX = 1, v = X.
0
Thread starter 6 years ago
#3
(Original post by Enginerd.)
"dv/dx=1 v=1"

This is wrong. If DV/DX = 1, v = X.
thats a typo i used v=x in my workings
0
Thread starter 6 years ago
#4
also can someone help me with this question
5ii, how did they get root 13
http://www.thestudentroom.co.uk/atta...9&d=1340294617
0
6 years ago
#5
Did you seriously divide x/x+2 into x/x + x/2?

Use substitution u=x+2
1
6 years ago
#6
(Original post by printergirl)
integrate ln(x+2) by parts
my working: u=lnx+2 du/dx =1/x+2, dv/dx=1 v=1 woops meant x
this makes
xln(x+2)-integral of x/x+2
i got xln(x+2)-x+0.25x2+c

however in the mark scheme it says this

is my answer the same? and if it is would i be awared the full marks
Why would

=
0
Thread starter 6 years ago
#7
(Original post by GeneralOJB)
Did you seriously divide x/x+2 into x/x + x/2?

Use substitution u=x+2
can you not do that?? edit oh i cbest made now than in the exam

can any1 do question 5ii, how did they get root 13
http://www.thestudentroom.co.uk/atta...9&d=1340294617

how do you split x/x+2
0
6 years ago
#8
(Original post by GeneralOJB)
Did you seriously divide x/x+2 into x/x + x/2?
Good spot

They had me baffled with that one
0
6 years ago
#9
(Original post by printergirl)
can you not do that??
How would you think that you can?
2
Thread starter 6 years ago
#10
(Original post by TenOfThem)
How would you think that you can?
how do i split it?
0
6 years ago
#11
(Original post by printergirl)
...
No need for the neg
It was a serious question

I was trying to find out what your misconception was
0
6 years ago
#12
(Original post by printergirl)
how do i split it?
You can't

Well, you can but you need to either use substitution or

(my preference)

Giving something that you can integrate

You can split the denominator but not the numerator
0
Thread starter 6 years ago
#13
(Original post by TenOfThem)
No need for the neg
It was a serious question

I was trying to find out what your misconception was
u seemed very rude

how do i split x/x+2 ????
0
6 years ago
#14
(Original post by printergirl)
u seemed very rude

how do i split x/x+2 ????
so do you

I have answered your question, there was no need to repeat
0
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