$$x^2{y}^2$$ $$\frac{x+y^2}{k+1}$$ $$x+y^{\frac{2}{k+1}}$$ $$\frac{a}{b/2}$$ $$a_0+\frac{1}{a_1+\frac{1}{a_2+\frac{1}{a_3+\frac{1}{a_4}}}}$$ $$\left(\genfrac{}{}{0ex}{}{n}{k/2}\right)$$ $$\left(\genfrac{}{}{0ex}{}{p}{2}\right)x^2{y}^{p-2}-\frac{1}{1-x}\frac{1}{1-x^2}$$ $$\underset{0<j<n}{\sum _{0\le i\le m}}P(i,j)$$ $$x^{2y}$$ $$\sum _{i=1}^p\sum _{j=1}^q\sum _{k=1}^r{a}_{ij}{b}_{jk}{c}_{ki}$$ $$\sqrt{1+\sqrt{1+\sqrt{1+\sqrt{1+\sqrt{1+\sqrt{1+\sqrt{1+x}}}}}}}$$ $$\left(\frac{{\partial }^2}{\partial x^2}+\frac{{\partial }^2}{\partial y^2}\right){\left|\right(x+\mathrm{i}y\left)\right|}^2=0$$ $$2^{2^{2^x}}$$ $$\underset{1}{\overset{x}{\int }}\frac{\mathrm{dt}}{t}$$ $$f\left(x\right)=\left\{\begin{array}{cc}1/3& \text{if}0\le x\le 1;\\ 2/3& \text{if}3\le x\le 4;\\ 0& \text{elsewhere.}\end{array}\right.$$ $$y_{x^2}$$ $$\sum _{p\text{prime}}f\left(p\right)=\underset{t>1}{\int }f\left(t\right)d\pi \left(t\right)$$ $$\left(\begin{array}{cc}\left(\begin{array}{cc}a& b\\ c& d\end{array}\right)& \left(\begin{array}{cc}e& f\\ g& h\end{array}\right)\\ 0& \left(\begin{array}{cc}i& j\\ k& l\end{array}\right)\end{array}\right)$$ $$det\left|\begin{array}{ccccc}{c}_0& c_1& c_2& ...& c_n\\ c_1& c_2& c_3& ...& c_{n+1}\\ c_2& c_3& c_4& ...& c_{n+2}\\ ...& ...& ...& & ...\\ c_n& c_{n+1}& c_{n+2}& ...& c_{2n}\end{array}\right|>0$$ $$y_{x_2}$$ $$x_{92}^{31415}+\pi$$ $$x_{y_b^a}^{z_c^d}$$