## Equation of Curve Reflected in Line x=c

What is the equation of the curve

$y=f(x)$
after reflection in the line
$x=k$
?
It is
$y=f(-(x-2k))$
.
For example
$y=x^2+2x$
when reflected in the line
$x=3$
becomes
$f(-(x-6))=(-(x-6))^3+2(-(x-6))=x^2-12x+36-2x+12=x^2-14x+48$
.