Question

2 term of arithematic sequence is 8 and common difference is 3.calculate sum of its first 12 term

Answer 1

Answer:

38

t2 = t1+ d

D= common difference

t1= 1st term

given t2= 8

D=3

8= t1+3

subtracting on both sides

we get t1=5

tn= t1+ ( n-1) D

t12= t1+11D

=5+11(3)

=5+33

=38

Answer 2

Answer:

step by step explanation

x2 = 8

d = 3

n th term = dn+( f-d)

x1 = x2-d

=8-3

=5

therefore 12 th term = 3×12+(5-3)

= 36+2

=38

Equation to find sum

n/2(x1+xn)

therefore,

12/2(5+38)

=6×43

=258

answer:-

Sum of its first 12 term =258

Check:-

Let's find the first 12 terms by adding common difference 3

x1= 5

x2= 8

x3= 8+3 =11

x4= 11+3= 14

...........................

.............etc.

answer:-

5+8+11+14+17+20+23+26+29+32+35+38= 258