Question

find the 4th term of an arithmetic sequence whose first term is -8 and whose 9th term is 32.

Answer 1

32-(-8) = 40 = 8d, so d = 5
-8+3*5 = 7

or,
T4 = T1 + 3*(T9-T1)/8

Answer 2

the ninth term is -8+(9-1)d and that is equal to 32. solve for d, then find the 4 term
A(4)=-8+d(4-1)