Prima di ogni figura ricordare di mettere
\documentclass[usenames,dvipsnames]{article}
\usepackage{pgfplots}
Prima figura
codice prima figura
\begin{tikzpicture}
\begin{axis}[
xtick = \empty,
ytick = \empty,
axis equal image,
axis x line=center,
axis y line=center,
xmin = -13,
xmax = 20,
ymin = -9.95,
ymax =15,
xlabel = {$x$},
ylabel = {$y$},
extra x ticks = {0},
extra x tick label = {$\hspace{-0.6cm}0$},
y label style={anchor=north east}
]
\addplot[very thick,samples=100,domain=12:-12,red] {4/3*x+4};
\draw (axis cs:9.5,8) node[red] {$y=\dfrac{4}{3}x+4$};
\addplot[very thick,samples=100,domain=12:-12,
blue] {-3/4*x+1/2};
\draw (axis cs:14,-4) node[
blue]{$y=-\dfrac{3}{4}x+\dfrac{1}{2}$};
\addplot[mark=*] coordinates {(2,-1)} node[below] {$A$};
\end{axis}
\end{tikzpicture}
seconda figura
codice seconda figura
\begin{tikzpicture}
\begin{axis}[
xtick = \empty,
ytick = \empty,
axis equal image,
axis x line=center,
axis y line=center,
xmin = -13,
xmax = 20,
ymin = -9.95,
ymax =15,
xlabel = {$x$},
ylabel = {$y$},
extra x ticks = {0},
extra x tick label = {$\hspace{-0.6cm}0$},
y label style={anchor=north east}
]
\addplot[very thick,samples=100,domain=12:-12,red] {4/3*x+4};
\draw (axis cs:9.5,8) node[red] {$y=\dfrac{4}{3}x+4$};
\addplot[very thick,samples=100,domain=-1.68:2,
blue] {-3/4*x+1/2};
\draw (axis cs:1,2) node[
blue]{$d$};
\addplot[mark=*] coordinates {(2,-1)} node[below] {$A$};
\end{axis}
\end{tikzpicture}
terza figura
codice terza figura
\begin{tikzpicture}
\begin{axis}[
width = 0.7\textwidth,
height = 0.7\textwidth,
xtick = \empty,
axis equal image,
ytick = \empty,
axis equal image,
axis x line=center,
axis y line=center,
xmin = -2,
xmax =3,
ymin = -2.5,
ymax = 2,
xlabel = {$x$},
ylabel = {$y$},
extra x ticks = {0},
extra x tick label = {$\hspace{-0.6cm}0$},
y label style={anchor=north east}
]
\draw[very thick,color=orange] (axis cs:1,-0.5) circle[radius=111];
\addplot[mark=*] coordinates {(1,-0.5)} node[below right] {$C$};
\draw (axis cs:1.3,1.5) node {$y=2x$};
\draw (axis cs:1.3,-1.8) node {$x^2+y^2-2x+y=0$};
\addplot[very thick,samples=100,domain=-1.68:2,
blue] {2*x};
\end{axis}
\end{tikzpicture}