how to find the point obtained by reflecting over a line? Given the point $A=(-2,6)$ and the line $y=2x$,what are the coordinates of the point B obtained by reflecting A over the line $y=2x$ ?
Can someone teach me how to solve this question please?

Note that AB has a gradient of $-\frac{1}{2}$, and that AB, which is $y=-\frac{1}{2}x+c$ intersects $y=2x$ at the midpoint of AB. 
Sub $(-2,6)$ into $y=-\frac{1}{2}x+c$, and solving, $c=5$.
Equate the two equations.
$-\frac{1}{2}x+5=2x$
Coordinates of midpoint of AB: $x=2$, $y=4$
Coordinates of B: $x=2+2+2=6$, $y=4-(6-4)=2$
