Author 
Topic 

ep6
Junior Member
USA
4 Posts 
Posted  09/27/2007 : 19:43:37

i have what seems to be two simple intergration problems but I cannot get the answer that the book says it is. I will first give the problems and what I got and see what you guys get and see what the book says
the first problem is
(x^(1/2))/x^(4/3) dx when I solve this i get x^(11/6)dx so that equals (6x^(5/6))/5 am I correct?
the second problem is
[(2/3 x^(3/2))(x^(1/2)]/4x^3 dx when i solve this i get 8/3 x^(4/2) dx so that equals 8x^(1)/3
Now both of those answers are incorrect accoring to my book. I know I make a lot of mistakes in these kind of problems. Can anyone tell me what I did wrong?



tkhunny
Advanced Member
USA
1001 Posts 
Posted  09/27/2007 : 23:27:02

[x^(1/2)]/[x^(4/3)]
[x^(3/6)]/[x^(8/6)]
[x^(11/6)] <== You missed a sign, but it doesn't seem to have mattered.
Somehow, you managed to get it right, anyway.
Good work and be more careful. 


ep6
Junior Member
USA
4 Posts 
Posted  09/27/2007 : 23:37:22

so is my intergration done right for the first problem? 


tkhunny
Advanced Member
USA
1001 Posts 
Posted  09/28/2007 : 08:25:58

This is where I start to get nervous.
1) You do it right in the first place. 2) You can't tell that it's right. 3) Someone tells you that it's right. 4) You STILL don't know that it's right.
Please gain some self confidence. Please learn to evaluate your work. Did you make any errors? Are you able to review your steps? Check all your signs and arithmetic.
You look at the second one and you tell me if it's right. 


Subhotosh Khan
Advanced Member
USA
9116 Posts 
Posted  09/28/2007 : 10:14:14

How can you tell whether you have derived the correct antiderivative of a function?
You find the derivative of your answer.
If the derivative is same as the original function  assuming you have done your differentiation correctly  you have found the correct antiderivative.
Using the principles above  tell us whether you have done the second problem correctly  or not.
I understand your confusion  the book said you were wrong  however, books have been known to be wrong. 



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