distance formula

(4, -12) and (12, -8)

Subtract the x's  in any order       [12- 4]   =  8      square this   = 64

Subtract the y's  in any order   [-8 - -12]  = [-8 + 12] = 4      square this  = 16

Add  the two squares   =   80

Take the square root  of   the last thing  =    sqrt(80)  = sqrt(16 * 5)  =  4sqrt(5)  units  is the distance