Question

The 54th and 4th term of an A. P are -61 and 64 respectively.Find 23rd term.

Answer 1

T54=a+53d=-61....1
T4=a+3d=64........2

on equating eq 1 and 2
we get
a=64-3d(from eq 2)

put value of a in eq 1

64-3d+53d=-61

50d=-61-64

d=-125

a=64+125x3=439

T23=439+22x-125

=439-2750
=-2311