Question

Find a30-a20 for the A.P -9,-14,-19-24,....

Answer 1

Answer:

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

Here,

a = first term = - 9

d = com. diff. = - 14 - (-9)

d = - 14 + 9 = - 5

Hence,

= > a$_{30}$ - a$_{20}$

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

= > a + 29d - a - 19d

= > 29d - 19d

= > 10d

= > 10(-5)

= > - 50