Question

What is the formula for getting an unknown number like the sum of four even number is something one of the no. Is given find the other three

Answer 1

2, 4, 6, 8
a=2
d=4-2=2
n=3
Tn=?

Tn= a+(n-1) d
2+(3-1) 2
2+2*2
2+4
6