First, we have to see how is the progression in the sequence and then we can make the formula for the n term
In the formula d is the constant change in one number to the other which means d=-5 and a1=25 which is the first term of the sequence
The expression inside the blue square box is the formula for the n term of the sequence, if you want to know any number , you just have to replce n for the position pof the number that you want to know.
