Question

初一数学题目-

1+2+3+……+(n-1)+n=

2+4+6+……+2n=

201+202+……+10000=

Answer 1

1`(1+n)*n/2
2`(2+2n)*n/2=(1+n)*n
3`(201+10000)*9800/2=49984900

Answer 2

1,
(1+n)n/2
2,
(1+n)n
3,
(201+10000)9800/2
=49984900

Answer 3

1`(1+n)*n/2
2`(2+2n)*n/2=(1+n)*n
3`(201+10000)*9800/2=49984900

Answer 4

1 n*(n+1)/2
2 n^2+n
3(201+000)*9800/2=49984900