Question

Find a1 in the arithmetic sequence for which d = -1 and a25 = -9

Answer 1

The \(n^{th}\) term of an arithmetic sequence is given by: \(\large a_n = a_1 + (n-1)d\)
Here, \(\large d = -1, n = 25, a_n = a_{25} = -9\).
Plug in the numbers and find \(\large a_1\)