Below a Question in Aviation SE I put a comment containing mathematical formulae. I had prepared the formulae using http://www.codecogs.com/latex/eqneditor.php. But it didn't become readable. Why? I paste below the results so you can understand:
I return on my second question. In order to have real solutions (\frac{T}{W}-G)^{2}-\frac{4*Cdo}{\pi ARe}\geq 0 . Then for simplicity of reasoning I define (\frac{T}{W}-G)=x and \frac{4*Cdo}{\pi ARe}=b . So the condition becomes x^{2}-b\geq 0 , but this (second grade) inequation is verified in both following zones: x\geq \sqrt{b} and also x\leq \left - \sqrt{b} \right i.e. \frac{T}{W}-G\geq 2\ast \ \sqrt{\frac{CD0}{\pi \ast AR\ast e}} and also \frac{T}{W}-G\leq-2\ast \ \sqrt{\frac{CD0}{\pi \ast AR\ast e}} . But Raymer exclude the second one, I don’t understand why.
$...$
(or$$...$$
for displayed equations). See, e.g., this fairly comprehensive guide from Mathematics.