Line L has the equation 4y-6x=33. Line M goes through the point A (5,6) and the point B (-4,k). Line L is perpendicular to M. Work out the value of k.
find the smallest sphere which touches the lines (x-2)/1=(y-1)/-2=(z-6)/1 and (x+3)/7=(y+3)/-6=(z+3)/1
Show that the two spheres x²+y²+z²+6y+2z+8=0 and x²+y²+z²+6x+8y+4z+20=0
are orthogonal.