documentclass{article}
usepackage[margin=2.4cm]{geometry}
usepackage{multicol}
usepackage{tikz}
usepackage{amsmath}
usepackage[no-math]{fontspec}
setmainfont{Times New Roman}
usetikzlibrary{arrows}
pagestyle{empty}

setlength{columnsep}{3cm}
begin{document}
begin{multicols}{2}

begin{enumerate}
item[9.] $xy=0Leftrightarrow x=0 ; text{or} ; y=0.$ the graph consist of the cordinate axes\

begin{tikzpicture}[>=triangle 45,x=0.5cm,y=0.5cm]
clip(-4,-4) rectangle (4,4);
draw [->] (0,-4.0) -- (0,4);
draw [->] (-4,0) -- (4,0);
draw [<-](0,1.5)--(1.5,2) node[anchor=west] {$xy=0$};
draw [->] (2.5,1.5) -- (1.8,0);
draw (4,0) node[anchor=north east] {$x$};
draw (0,4) node[anchor=north east] {$y$};
draw (0,0) node[anchor=north east] {$0$};
end{tikzpicture}

item[10.] $|y|=1 Leftrightarrow y=1 ;text{or} ; y=-1$\
vspace{5mm}

begin{tikzpicture}[>=triangle 45,x=0.5cm,y=0.5cm]
clip(-4,-4) rectangle (4,4);
draw [->] (0,-4.0) -- (0,4);
draw [->] (-4,0) -- (4,0);
draw (-4,2)--(0,2)node[anchor=north east] {$1$}--(4,2);
draw (-4,-2)--(0,-2)node[anchor=north east] {$-1$}--(4,-2);
draw (2,1)  node {$|y|=1$};
draw (4,0) node[anchor=north east] {$x$};
draw (0,4) node[anchor=north east] {$y$};
draw (0,0) node[anchor=north east] {$0$};

end{tikzpicture}
end{enumerate}
end{multicols}
begin{enumerate}
item[11.]By the point-slop form of the equation of a line, an equation of the line throuth $(2,-3)$ with slope $6$ is\
$y-(-3)=6(x-2)quad text{or} quad y=6x-15.$
item[12.]$y-(-5)=-frac{7}{2}[x-(-3)]quad text{or} quad y=-frac{7}{2}x-frac{31}{2}$
item[13.]The slope of the line throuth $(2,2)$ and $(1,6)$ is $m=dfrac{6-1}{1-2}=-5$, so an equation of the line is \
$y-1=-5(x-2)quad text{or} quad y=-5x+11.$
item[14.]For $-1,-2)$ and $(4,3)$, $m=dfrac{3-(-2)}{4-(-1)}=1$.An equation of the line is $y-3=1(x-4);text{or}; y=x-1.$
end{enumerate}
end{document}