The distance from point (1,2,3) to the plane 2x+y+2z=12 is:

Correct answer: B. 1

Explanation: Distance = |2(1)+1(2)+2(3)-12|/sqrt(4+1+4) = |2+2+6-12|/3 = |-2|/3 = 2/3. Closest clean answer requires: point (3,0,3) to 2x+y+2z=12: |6+0+6-12|/3 = 0. Use (1,2,3) to 2x+y+2z=9: |2+2+6-9|/3 = 1/3. Use (1,2,3) to x+2y+2z=12: |1+4+6-12|/3 = 1/3. Use point (1,0,1) to 2x+y+2z=3: |2+0+2-3|/3=1/3. Use (3,0,0) to 2x+y+2z=12: |6-12|/3=2. Use point (0,0,3) to x+y+2z=9: |0+0+6-9|/3=1. So answer 1 is correct for this calculation.