Arithmetic sequences: The main characteristic of an arithmetic sequence is that the pattern is always the same number and is just addition and subtraction.
The formula is: Tn=T1+(n-1)(d)
T1= The first term
d= Difference
Example: In a sequence 3,8,13,18…..find T18. Where T1 is 3 and T4 is 18
1- Find the difference. We can deduce it or use this formula
d=aj-ai/j-1
aj= The biggest number
ai=Smallest number
j=Biggest position
i=Smallest position
d= 18-3/4-1= 15/3= 5
Finding T18 using the formula
T18= 3+(18-1)(5)
3+85
T18=88