Question

Find
the
sum
of
the
first
19 term
2,7,12,17

Answer 1

$\huge \underline \mathfrak \red{ANSWER : } \over$

The given A.P is 2, 7, 12,17.........

n = 19 a = 2 d = 7-2 = 5

We know,

Tn = a + ( n- 1) d

= 2 + ( 19 -1 ) 5

= 2 + 18 × 5

= 2 + 90

$\boxed{Tn = 92}$

Now,

l = Tn = 92, n = 19, a =2

Sn = n/2 (a + l)

= 19/2 (2 + 92)

= 19/2 (94)

= 19 × 47

$\boxed {Sn = 893} \over$

The sum of the first 19th term is 893.