如图1,曲线表示某池塘中浮萍蔓延的面积y(m~2)与时间t(月)的关系:y=a~t,对此有以下叙述,其中正确的有____.(1)这个指数函数的底数为2;(2)第5个月时,浮萍面积就会超过30 m~2;(3)浮萍由4 m~2蔓延到12 m~2需要经过1.5个月;(4)浮萍每月增加的面积都相等;(5)若浮萍蔓延到2 m~2、3 m~2、6 m~2所经过的时间分别为t_1、t_2、t_3,则t_1+t_2= As shown in Fig. 1, the curve shows the relationship between the area y (m ~ 2) and the time t (month) of duckweed spreading in a pond: y = a ~ t, which is described below, ) The base of this exponential function is 2; (2) Duckweed area will exceed 30 m ~ 2 at the 5th month; (3) Duckweed will spread from 4 m ~ 2 to 12 m ~ 2 after 1.5 months ; (4) the area of ​​duckweed added each month is equal; (5) if the duckweed spread to 2 m ~ 2, 3 m ~ 2, 6 m ~ 2 time t_1, t_2, t_3 respectively, then t_1 + t_2 =