Image of the point (–1, 3) with respect to the line $y=2x$ is

Equation of the line through (–1, 3) perpendicular

to $y=2x$is $x+2y=5$ which mets $y=2x$ at 

(1, 2). Required point is $(\alpha ,\beta )$ such that $\frac{\alpha -1}{2}=1,$

$\frac{\beta +3}{2}=2$.