]> $x^2{y}^2$ $\frac{x+y^2}{k+1}$ $x+y^{\frac{2}{k+1}}$ $\frac{a}{b/2}$ $a_0+\frac{1}{a_1+\frac{1}{a_2+\frac{1}{a_3+\frac{1}{a_4}}}}$ $\left(\begin{array}{c}n\\ k/2\end{array}\right)$ $\left(\begin{array}{c}p\\ 2\end{array}\right)x^2{y}^{p-2}-\frac{1}{1-x}\frac{1}{1-x^2}$ $\underset{0<j<n}{\sum _{0\le i\le m}}P(i,j)$ $x^{2y}$ $\sum _{i=1}^p\sum _{j=1}^q\sum _{k=1}^r{a}_{ij}{b}_{jk}{c}_{ki}$ $\sqrt{1+\sqrt{1+\sqrt{1+\sqrt{1+\sqrt{1+\sqrt{1+\sqrt{1+x}}}}}}}$ $\left(\frac{{\partial }^2}{\partial x^2}+\frac{{\partial }^2}{\partial y^2}\right){\left|\right(x+\mathrm{i}y\left)\right|}^2=0$ $2^{2^{2^x}}$ $\underset{1}{\overset{x}{\int }}\frac{\mathrm{dt}}{t}$ $\underset{D}{\iint }\mathrm{dx}\mathrm{dy}$ $f\left(x\right)=\left\{\begin{array}{cc}1/3& \text{if}0\le x\le 1;\\ 2/3& \text{if}3\le x\le 4;\\ 0& \text{elsewhere.}\end{array}\right.$ $\stackrel{k\text{times}}{\overbracket{x+\cdots +x}}$ $y_{x^2}$ $\sum _{p\text{prime}}f\left(p\right)=\underset{t>1}{\int }f\left(t\right)d\pi \left(t\right)$ $\left\{\underset{k+\mathrm{\ell }\text{elements}}{\underbracket{\stackrel{ka\text{'s}}{\overbracket{a,...,a}},\stackrel{\mathrm{\ell }b\text{'s}}{\overbracket{b,...,b}}}}\right\}$ $\left(\begin{array}{cc}\left(\begin{array}{cc}a& b\\ c& d\end{array}\right)& \left(\begin{array}{cc}e& f\\ g& h\end{array}\right)\\ 0& \left(\begin{array}{cc}i& j\\ k& l\end{array}\right)\end{array}\right)$ $det\left|\begin{array}{ccccc}{c}_0& c_1& c_2& \cdots & c_n\\ c_1& c_2& c_3& \cdots & c_{n+1}\\ c_2& c_3& c_4& \cdots & c_{n+2}\\ ⋮& ⋮& ⋮& & ⋮\\ c_n& c_{n+1}& c_{n+2}& \cdots & c_{2n}\end{array}\right|>0$ $y_{x_2}$ $x_{92}^{31415}+\pi$ $x_{y_b^a}^{z_c^d}$ $y_3^{‴}$