Question

the 13th term of a. p is 3 and the sum of first 13 terms is 234. find the common differendifference and the sum of first 21 terms

Answer 1

Step-by-step explanation:

given 13th term is 3

so a+12d =3 [a is first term and d is difference]

and sum is 234

so n/2[2a+(n-1)d]=234

after equating we get a +6d = 36

so a+12d= 3

a+6d=36

after equating we get d= -33/6 and a= -63