求助呀~~~GWD1套 数学10,28,29

luluicecream

是t=-1哦， 不是t+2=-1.

只能往上面推，t=-1, t+2=1

t=1, t+2=3,

t=3, t+2=5.

根据条件不可以推出-3的。

luluicecream

"sum of all the even numbers"

"the first n positive integers equals[n(n+1)]/2."

The formula given is not for "sum of all EVEN numbers", it's for "ALL" first n positive integers.

luluicecream

1982~ 1987, 5 years, 1984 is leap year.

5 * 365 +1 =1862

1862/7 (7 days/week)  Reminder:6.

Friday+6 days = Sat., Sun., Mon., Tue., Wed., Thur.


Answer= Thursday.