Question

Find the 75th term of the arithmetic sequence -1, 15, 31, ...−1,15,31,

Answer 1

Answer:

a = -1

d= a2 - a1= 15- (-1)= 15+1 =16

n = 75

an = a +(n-1)d

a75 = (-1) + (75-1)(16)

= -1+1184

a75 = 1183

Answer 2

Answer:

First term(a) = -1

Common difference(d) = 16

75th term = a + 74×d

= -1 + 74×16

= 1184 - 1

= 1183