find the distance of a point from a line?

**i'm truly sorry if this is the wrong forum, as i'm teaching myself this stuff, i'm unsure of what it's sub forum should be. since my last question was moved here, i put this one here too.**

anyway.....

use the following procedure to find the leats ( perpendicular ) distance of the point *( 1,2 )* from the line *y = 3x + 5*, without having to find the equation of a line perpendicular to *y = 3x + 5*.

(a) let *( x,y )* be a general point on the line, Show that its distance, *d*, from *( 1,2 )* is given by *d^2 = ( x - 1 )^2 + ( y - 2 )^2*.

(b) use the equation of the line to show that *d^2 = ( x - 1 )^2 + ( 3x 3 )^2*. I CAN SEE THE ANSWER HERE SO NO WORRIES.

(c) by completing the square, show that the minimum distance required 3/5√10