Hello,

I had this problem:

I know the correct answer but I don't understand EXACTLY why this is incorrect:

I understand it has something to do with the integral "in regards to x" (because we write the dx) there, but could you explain that to me a little better please?

Thanks a lot!

Thanks to Wolfram I avoided sending a wrong answer in this on my homework.(really powerful tool, too bad we can't use the internet on tests (but we can use it in real life though...))