to get the y-intercept of any function, we simply set x = 0 and solve for "y", bearing in mind that x = 0 at that point.
[tex]\bf \stackrel{f(x)}{y}=2x\implies y=2(\stackrel{\stackrel{x}{\downarrow }}{0})\implies y=0~\hfill \blacktriangleright (0,0) \blacktriangleleft\\\\\\~\hspace{32em}[/tex]