Answer:
an = -773 + 48n
Explanation:
an = a + (n -1)d
a15 = a + (15 - 1)d = -53
a + 14d = -53 .........1
a16 = a + (16 - 1)d = -5
a + 15d = -5 ............2
subtract equation 2 from 1
a - a + 14d - 15d = -53 + 5
-d = -48
d =48
substitute d =48 in equation 1
a + 14(48) = -53
a +672 = -53
a = -53 -672
a = -725
an = -725 + (n -1)48
an = -725 + 48n - 48
an = -773 +48n