Question

The first and last term of an AP are -3 and 145 , respectively .If the common difference is 4 Find the 12th ,25th and the number of the term in the AP

Answer 1

Tn = a + (n-1) d

a = -3
d = 4
Tlast = -3 + (n-1)*4 = -3 + 4 n - 4 = -7 + 4 n = 145
so
4 n = 152
n = 38 terms total
T12 = -3 + 11*4
T25 = -3 + 24*4