Question

The 3rd 15th and the last term of an A.P is 4, 8 and 18 respectively. Find the first term,

common difference and number of term. pls explain full​

Answer 1

Hey mate here is ur answer

2

I hope this helps u out

Answer 2

nth term of an ap is given by the equation => a + (n-1)d


• given 3rd => 4 so ,


4= a+ 2d ————(1)


• 8 = a + 14d ———-(2)

(2)-(1) ==> 4 = 12d
====> 4/12 = d
======> d = 1/3



now substitute d in (1) , 4 = a + 2/3

a = 4-2/3
a = 12-2/3 = 10/3



for last term

18 = a + (n-1)d
18= 10/3 +(n-1)1/3

18-10/3 = (n-1)1/3
44/3 = n-1 x 1/3

cancel out 1/3 in both sides

44 = n-1
n ==> 45 //



hope this helps