in the arithmetic sequence u₈ = 10, u₉ = 12, find the first term

Answer 1

u8 = 10

u10 = 12

common difference = d = 12-10 = 2

u7= 8

u6=6

u5 = 4

u4 = 2

u3 = 0

u2 = -2

u1 =-4

un = u1 + (n-1)d

the nth term = the 1st term + (n-1) x the common difference

Answer 2

-4; If 10 is the eighth term and 12 is the ninth term, the difference between consecutive terms must be 2. (In an arithmetic sequence, the difference between consecutive terms is constant.) Therefore, the first term is the result of counting backwards by 2 from 10 seven times. (i.e. 10 - 7 * 2)

-4 -2 0 2 4 6 8 10 12

1 2 3 4 5 6 7 8 9