Question

plz this too answer it in need​

Answer 1

Answer;

n=37

Middle term =  37+1/2

                    =19

T18+T19+T20=225

Last 3 terms =35th,36th,37th

T35+T36+T37=429

⇒a+17d+a+18d+a+19d=225

⇒3a+54d=225

⇒a+8d=75

⇒a=75−18d

⇒a+34d+a+35d+a+36d=429

⇒3a+105d=429

⇒a+35d=143

⇒75−18d+35d=143

⇒17d=68

d=4

a=75−18(4)

=3

AP=3,7,11,15,19,.....

HOPE IT HELPS YOU