now, bear in mind that all these ones are lines, and to graph a line all you need is two points, so let's pick a couple of random values for say "x" and let's see what we get for "y" and that's our x,y point.
3)
[tex]9x+4y=-16\implies \stackrel{\textit{using x = 0}~\hfill }{9(0)+4y=-16}\implies 4y=-16 \\\\\\ y=\cfrac{-16}{4}\implies y=-4~\hspace{10em}(0~~,~~-4) \\\\[-0.35em] ~\dotfill\\\\ 9x+4y=-16\implies \stackrel{\textit{using x = -4}~\hfill }{9(-4)+4y=-16}\implies -36+4y=-16 \\\\\\ 4y=20\implies y = \cfrac{20}{4}\implies y = 5~\hspace{10em}(-4~~,~~5)[/tex]
check the red line in the picture below.
4)
[tex]5x+2y=8\implies \stackrel{\textit{using x = 0}~\hfill }{5(0)+2y=8}\implies 2y=8\implies y=\cfrac{8}{2}\implies y=4 \\\\\\ ~\hspace{10em}~\hspace{10em}(0~~,~~4) \\\\\\ 5x+2y=8\implies \stackrel{\textit{using x = 4}~\hfill }{5(4)+2y=8}\implies 20+2y=8\implies 2y=-12 \\\\\\ y=\cfrac{-12}{2}\implies y=-6~\hspace{10em}(4~~,~~-6)[/tex]
check the blue line in the picture below.
