Integral equation I don't understand

[anicca]

I don't understand the equation shared at this link that I'm studying.

I understand that in line 2 he multiplies and divides by the same integral, but in the last line a reformulation happens and I don't get the properties used to obtain that.

Thanks in advance

 

[tkhunny]

You're going to have to learn to communicate in some other way. Clicking a random link is not usually a good plan.

 

[anicca]

 

[anicca]

thanks for pointing out, sorry