The nnnth term of an AP is an=5−2na_n = 5 - 2nan=5−2n. Find a1a_1a1, the common difference ddd, and S20S_{20}S20.
a1=3, d=−2, S20=−340a_1=3,\ d=-2,\ S_{20}=-340a1=3, d=−2, S20=−340
a1=5, d=−2, S20=−340a_1=5,\ d=-2,\ S_{20}=-340a1=5, d=−2, S20=−340
a1=3, d=2, S20=460a_1=3,\ d=2,\ S_{20}=460a1=3, d=2, S20=460
a1=3, d=−2, S20=−360a_1=3,\ d=-2,\ S_{20}=-360a1=3, d=−2, S20=−360