Basic Equation question

Question

This is regarding algorith complexity, but that's not the point here.

I saw this resolution:

4( n/1,3 )² = 4/1,69 x n² 

Could anyone clarify how is this equation is done? How can 4( n/1,3 )² equals to 4/1,69 x n²

I tried to reproduce but failed drastically.

4( n/1,3 )²  =  4 x n/1,3 x n/1,3
             =  4 x n²/1,69
             =  ?

Thanks in advance.

Answer 1

$$ (a+b)^2=a^2+b^2+2ab \\(1.3)^2=(1+0.3)^2=1+(0.3)^2+2(1)(0.3)\\(1.3)^2=1+0.09+0.6=1.69 \\so\\4(\frac{n}{1.3})^2=4*\frac{(n)^2}{(1.3)^2}=4*\frac{n^2}{1.69} $$