I know this comment is from a year ago but to anyone wondering the same thing, think of ‘r’ as r/1 then multiply. The r only gets distributed into the numerator not denominator
9x3/2 is 27/2. not 6. 9x 2/3 is 6. root13.5/pi= ~2 I got r to be 2.07 and h to be 0.43. which makes sense when substituted back to the surface equation , it equals 18.
