Question

find the 20th term of AP
-5,-5/2,0,5/2,...................

Answer 1

A.P ⇒ -5 , -5/2 , 0 , 5/2 , 5

a = -5
d = a2 - a1 = -5/2 - ( - 5 )
= -5/2 + 5

∴ d = 5/2
n = 20
an = ?
Now,
∵ an = a + ( n - 1 )d
∴ a 20 = -5 + ( 20 - 1 ) * 5/2
a 20 = -5 + 19 * 5/2
a 20 = -5 + 47.5

∴ a 20 = 42.5

∴ The 20th term of the given A.P is 42.5 

Hope this helps you !!
# Dhruvsh