latex

\usepackage{amsmath}
\usepackage{amssymb}

%in document
\[
F(x) = \left\{
\begin{array}{ll}
x^2 + y - 25x, & \text{if } x > 0;\\
x^3 - 3y + 7, & \text{if } {-25}\leqslant x \leqslant 0;\\
x + 2y^2, & \text{if } x<{-25};
\end{array}
\right\}
\]

\[
F(x) =
\begin{cases}
x^2 + y - 25x, & \text{if } x > 0;\\
x^3 - 3y + 7, & \text{if } {-25}\leqslant x \leqslant 0;\\
x + 2y^2, & \text{if } x<{-25};
\end{cases}
,\qquad \text{where } y = \alpha ^ {\gamma}
\]

\begin{gather}
x(t) = x_A + (x_B - x_A)\cdot t \\
y(t) = y_A + (y_B - y_A)\cdot t \\
z(t) = z_A + (z_B - z_A)\cdot t
\end{gather}

\begin{gather*}
x(t) = x_A + (x_B - x_A)\cdot t \\
y(t) = y_A + (y_B - y_A)\cdot t \\
z(t) = z_A + (z_B - z_A)\cdot t
\end{gather*}

\begin{gather}
x(t) = x_A + (x_B - x_A)\cdot t \label{eq:1} \\
y(t) = y_A + (y_B - y_A)\cdot t \label{eq:2} \\
z(t) = z_A + (z_B - z_A)\cdot \label{eq:3}t
\end{gather}

 %\eqref{eq:3}

\begin{equation} \left\{
\begin{gathered}
x(t) = x_A + (x_B - x_A)\cdot t \\
y(t) = y_A + (y_B - y_A)\cdot t
\end{gathered}
\right.
\end{equation}

\begin{align}
a = & 25, & b = & 38, & c = & 56, \\
d = & 325, & f = & 238, & e = & 156
\end{align}

\begin{align*}
a ={}& 25, & b ={}& 38, & c ={}& 56, \\
& & f &= 238, & e &= 156
\end{align*}

\begin{equation}
\begin{aligned}
a ={}& 25, & b ={}& 38, & c ={}& 56, \\
& & f &= 238, & e &= 156
\end{aligned}
\end{equation}

\begin{multline}
Tran(a,b,c,d) = a^b + \cos \frac ba - \sin \frac c d + \|a^2 + b^3 - c^4 \| + \\ + lim_{x \to \infty}{\frac {a^x + \log b}{b! + x!}} - trop(b, a, d)^{tr(b,a,c)} + \sum_{i = 1}^{\infty} \frac{a^{}}{a!+b!} = \\= \Gamma(a, b) + \psi(a, b^d) - \prod_{j = 1}^{\infty}\sum_{k = 0}^{i^k}
\end{multline}