Question

sliday
Additional
Question
1. The 21st
torm
of the A.P
the A.P whose
terms are - 3 and 4 is
2. If common difference of an A. p is 5, then
is
first two
A18
as 3​

Answer 1

Step-by-step explanation:

1. 137

The 21st term of an AP is 137. Step-bystepexplanation: It is given that first two term are -3 and 4. Therefore the 21st term of an AP is 137.

2. Given, the common difference of AP i.e., d = 5

Now, a18 - a13 = a + (18-1) d - [a+(13-1)d] [∵an = a + (n-1)d]

= a + 17 × 5 - a - 12 × 5

= 85 - 60 = 25

Answer 2

Answer:

1. Given, first two terms of an AP are a = -3 and a + d = 4.

`implies -3+d=4`

Common difference, `d=7`

` :. a_(21)=a+(21-1)d " " [ :' a_(n)=a+(n-1)d]`

` " " = -3+(20)7`

` " " =-3+140= 137`

2. An = a + ( n -1 ) d

d = 5 { Given }

Here a is ist term and d is common Difference.

A18 = a + ( 18 - 1 ) ×5

A18 = a + 17×5

And

A13 = a + ( 13 -1 ) ×5

A13 = a + 12 ×5

So,

A18 - A13 = a + 85 - a - 60

A18 - A13 = 25.