Melody

You cannot expect people to answer questions which are not complete.

Concentrate on working out how to post a picture.

I have 5 different biology textbooks and 4 different economics textbooks. In how many ways can I place the 9 textbooks on a bookshelf, in a row, if there must be an economics textbook in the middle, and there must be a biology textbook at each end?

B1 B2 B3 B4 B5     E1 E2 E3 E4

B***E***B 

5 * 4 * 4 * 6! = 57600   

You have given an excellent answer Leo !

You need to add brackets. I have no idea what your question is.

Oh

Is it       

integral of e^(1/x) / (x^2) dx    ? 

Hi Hugo,

Do not worry this time but in the future, if you can find it easily, please add the address of the alternate post. (In a link)

This is more for the benefit of other users than it is for the asker of the question.

Thanks.