Inline math: $$ \varphi = \dfrac{1+\sqrt5}{2}= 1.6180339887… $$
renders to
Inline math: $$ \varphi = \dfrac{1+\sqrt5}{2}= 1.6180339887… $$
Block math:
$$
\varphi = 1+\frac{1} {1+\frac{1} {1+\frac{1} {1+\cdots} } }
\varphi = \sqrt5{2}= 1.6180339887…
$$
renders to
$$ \varphi = 1+\frac{1} {1+\frac{1} {1+\frac{1} {1+\cdots} } } \varphi = \sqrt5{2}= 1.6180339887… $$