Ok, the problem is simple enough, I think. I just think I'm missing something obvious.
I have an equation involving the scale factor R(t) and need to integrate it.
I am at the first equation and need to get to the second by integrating (with respect of R, I suppose)
The Attempt at a Solution
I tried integrating wrt R and the solution is right except that I have a term too many. It seems that the first term, the one with the double dotted R, just disappears after integration?
I am puzzled by that.
I don't know where it goes and why.
The other terms, as I said, are right.
PS: the first equation is right, as I was asked to show something.