Okay, here we have this:
Considering the sequence 10, 20, 30, 40, 50; let's identify the difference between each term:
20-10=10
30-20=10
40-30=10
50-40=10
Here we can see that the difference is always the same, so we obtain the following function:
a(n)=a1+d(n-1) (Where "n" is the position of the term of the sequence that we want to know)
a(n)=10+10(n-1)
For example, let's find the 5th term of the sequence, so we need to replace n with 5:
a(n)=10+10(n-1)
a(n)=10+10(n-1)
a(5)=10+10(5-1)
a(5)=10+10(4)
a(5)=10+40
a(5)=50
Here we obtain that the 5th term of the sequence is 50.