Question

If 6th and 14th terms of an A.P. are 29 and 69 respectively, then its 21st term is

Answer 1

Answer:

149

Step-by-step explanation:

nth term = a+(n-1)d

6th term = a+(6-1)d=29

                  a+(6-1)d=29

                  a+5d=29 __________eq1

                 

14th term = a+(14-1)d=69

                  a+(14-1)d=69

                   a+13d=69__________eq2

eq2-eq1

a+13d-(a+5d)=69-29

a+13d-a-5d=40

8d=40

d=8

putting d=8 in eq1

a+5(8)=29

a+40=29

a=29-40

a= -11

21th term = a+(21-1)d

                =-11+(20)8

                 = -11+160

                  =149