Hi, I want to confirm this: a=8, b=5, c=7 Count out the distance from origo to planet z = ax + by + c in three different ways. 1) With the aid of linear algebra and geometry (no derivates!). Normalvector is: (a,b,-1) , the length * (8,5,1) = p ,(p=point) p=(x,y,z) gives 8s=x , 5s=y. -s = 8x+5y+7 => -90s=7 => s=-7/90 => x = -56/90 , y = -35/90 , z = 7/90 , Is this correct? 2) Through solving one optimization problem in two variables without bee conditions. q^2 = (ax+by+c)^2 where q is the distance uses the df/dx = df/dy = 0 and gets: 130x+80y+112=0 80x+52y+70=0 and then solves what x,y,z is ? Or have i done something wrong? 3) Through using Lagranges multiplier method I havent done this because i dont know how to use this method, can anyone help me with this? I want some help to confirm if i am solving this correctly.