Number 2, 7, 15, 26, 40. (n) what is the law, find out the algebraic formula
a1=2
a2=7
a3=15
…
a2-a1=5
a3-a2=8
a4-a3=11
……
8-5=11-8=14-11=…… =3
introduction
an=a1+ [10+3(n-2)](n-1)/2 =3/2(n^2)+(1/2)n
3 / 4, 9 / 8, 15 / 16, 21 / 24, () fill in the regular number
3 / 4, 9 / 8, 15 / 16, 21 / 24, () fill in the regular number
The answer is 27 / 36
The data is divided into numerator and denominator;
The molecules are 3, 9, 15 and 21, and the rule is f (n) = 3 * (2n-1)
The denominator is 4,8,16,24, and the rule is f (n) = f (n-2) + F (n-1) + 4 * (4-N)
Fill in 6 7 9 12 16 〔 2 3 5 8 13 21 〕
6 7 9 12 16 【21】
6+1=7
7+2=9
9+3=12
12+4=16
16+5=21
2 3 5 8 13 21 【 34】
2+3=5
3+5=8
5+8=13
8+13=21
13+21=34