Answer:
[tex]y = -2\, x[/tex].
Step-by-step explanation:
Find two points on the original line, [tex]y = 2\, x[/tex]:
Setting [tex]x = 0[/tex] gives [tex]y = 0[/tex], which corresponds to the point [tex](0,\, 0)[/tex].
Setting [tex]x = 1[/tex] gives [tex]y = 2[/tex], which corresponds to the point [tex](1,\, 2)[/tex].
Reflect the two points with respect to the [tex]y[/tex]-axis by inverting the [tex]x[/tex]-coordinate of each point. The point [tex](0,\, 0)[/tex] stays the same, whereas the point [tex](1,\, 2)[/tex] would be mapped to [tex](-1,\, 2)[/tex].
Find the equation of the new line. The slope of the new line would be:
[tex]\begin{aligned}\frac{2 - 0}{(-1) - 0} = \frac{2}{(-1)} = -2\end{aligned}[/tex].
Equation of the new line in point-slope form:
[tex]y - 0 = (-2)\, (x - 0)[/tex].
[tex]y = -2\, x[/tex].
