设一楼有X个房间,住X^2人；那么二楼有(X+1)个房间,住[(X+1)^2-(X+1)]人；依题意得：X^2+[(X+1)^2-(X+1)]=36 解得：X1=4;X2=-9/2(舍去),即：
二楼有房间：X+1=4+1=5个.