Step-by-step explanation:
We can find r by dividing the second term of the series by the first. Substitute values for a 1 , r , a n d n \displaystyle {a}_{1}, r, \text{and} n a1,r,andn into the formula and simplify. Find a1 by substituting k = 1 \displaystyle k=1 k=1 into the given explicit formula.
