There are several ways to use latex in blogger. Here I present the one I believe the best, MathJax.
1. add Gadget -> JavaScript/HTML
2. do not fill in title, copy the following lines into the content part:
examples:
I. Newton: $\mathbf{F} = m\cdot\mathbf{a}, f = -\frac{G m_1 m_2}{r^2}.$
J. Maxwell: $\partial_\nu F^{\mu \nu} = \mu_0 J^\mu$; $\epsilon^{\mu \nu \sigma \rho} \partial_\nu F_{\sigma \rho} = 0$.
J. Gibbs: $ \rho \propto e^{-\beta (H - \mu N)}$.
A. Einstein: $\frac{d}{d\tau}p^\mu = f^\mu, G^{\mu \nu} = \frac{8 \pi G}{c^4} T^{\mu \nu}.$
E. Schrodinger: $ i\hbar \frac{\partial}{\partial t}\left. |\psi\right> = H \left.| \psi \right>, G_{\mu\nu} = \frac{ 8 \pi G }{ c^4 } \left\langle \hat T_{\mu\nu} \right\rangle_\psi$
R. Feynman: \[
D_F(x - x') = \int \mathcal{D}\varphi \; \exp \left\{ \frac{i}{\hbar} S[\varphi] \right\}.
\]
J. Schwinger: \[
\left\{
\frac{\delta}{\delta \varphi(x)} S\left[ \frac{1}{i}\frac{\delta}{\delta J} \right] + J(x) \right\} \int \mathcal{D}\varphi \; \exp\left( \frac{i}{\hbar}S[\varphi, J] \right) = 0.
\]
