Answer:1.n2+n = n (n+1) 2.109 3.4.150 minutes 5.c6.d7.b8.b9. (1) s = N= 15 10。 ( 1)a = . 1 1。 S = 4n-4 12。 B2 13.595。 (65438 (2)4n+2 15。 A let a natural number start from a+ 1, and the sum of these 100 consecutive natural numbers is (a+ 1)+(a+2)+? ... =100) =100a+5050.16.c The first column number can be expressed as 2m+ 1, and the second column number as 5n+ 1, from 2m+/kloc ... 1000 18.d tip: each student moves bricks once an hour, and C students move bricks once an hour, which is the speed. 19. Hint: a 1= 1, a2=, a3=, an=, the original formula = .20. Then 100(x+3y)=80(x+5y) and x=5y, then you can buy a calculator = 160 (set) and a book =800 (book). (2) If it can be divided into six pieces of paper that meet the requirements, the sum of its areas should still be 65438. But the sum of the areas of the above six rectangles is/kloc-0 /×1+/kloc-0 /× 2+/kloc-0 /× 3+/kloc-0 /× 4+2× 2+/kloc-0 /× 5 =19. So split it into six parts? It is impossible to get a piece of paper that meets the requirements.