Question

For the A.P.: -3, -7, -11,..., can we find a30 - a20 without actually finding a30 and a20? Give reasons for your answer

Answer 1

Answer:

- 40

Step-by-step explanation:

Yes, it's possible.

 nth term of any AP is given by a + ( n - 1 )d, where a is the first term and d is the common difference.

In this manner,

 a₃₀ - a₂₀ = [ a + ( 30 - 1 )d ] - [ a + ( 20 - 1 )d ]

   ⇒ a + 29d - [ a + 19d ]

   ⇒ a + 29d - a - 19d

   ⇒ 10d

Hence, we just have to find the common difference.

Here,

d = co. di. = - 7 - ( - 3 ) = - 4

 Hence,

a₃₀ - a₂₀ = 10d = 10( - 4 )

              = - 40

Answer 2

Answer:

-40

Step-by-step explanation:

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