Question

the difference between the 4th and 11th terms of an A.P is twice the sum of the first 2 terms. if the first term is 5,find the 20th term​

Answer 1

Step-by-step explanation:

a11-a4=2(a1+a2)

a+10d-a-3d=2(5+5+d) (a2=a+d)

7d=20+2d

5d=20

d=4

a20=a+19d

a20=5+19*4

a20=5+76

a20=81

Answer 2

answer= 81

given

2{a+(a+d)}= a+10d-(a+3d)

here, a= 5

20+2d=7d

d= 4

20th term = a+19d

= 5+19×4

=81