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Problem solving an integral with Wolfram|Alpha?

Posted 10 years ago

Hi, today i was solving some math problems with integrals and wolfram alpha (windows 10 app version) gave me an answer that i think is incorrect, could this be possible? Here is the (i think wrong) result: http://s17.postimg.org/hg54ttf4u/Result.jpg After that i checked on another integral calculator and it gave me this result: http://s22.postimg.org/t1z74y041/Result_2.png which i think its correct. Can someone tell me if i am right or if i am ignoring something?

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POSTED BY: Rodrigo Viana
3 Replies

Hi,

that is the step by step solution. This also works:

FullSimplify[1/2 Log[x + 2] - (Evaluate@Integrate[1/(2 x + 4), x]), Assumptions -> x > -1]

It gives

-(Log[2]/2)

so a constant which obviously equals

-(-(Log[2]/2) + Log[4]/2)

You can also do:

1/2 Log[x + 2] + Log[2]/2 == (Evaluate@Integrate[1/(2 x + 4), x]) // FullSimplify

or evaluate the derivatives:

FullSimplify[D[1/2 Log[x + 2], x] == D[(Evaluate@Integrate[1/(2 x + 4), x]), x]]

Cheers,

M.

POSTED BY: Marco Thiel
POSTED BY: Marco Thiel
Posted 10 years ago

Thank you very much for the explanation!

POSTED BY: Rodrigo Viana
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