Question

the first term of an AP is a and common difference is d. then what are the first five terms of that AP..... please answer........​

Answer 1

ANSWER

Here the first term a=3 and common difference d=4.

Now a  

n

​  

=a+(n−1)d

∴a  

1

​  

=a=3

a  

2

​  

=a+d=3+4=7

a  

3

​  

=a+2d=3+2×4=11

a  

4

​  

=a+3d=3+3×4=15

a  

5

​  

=a+4d=3+4×4=19

∴ series in A.P. is 3,7,11,15,19,......

Thus, the sum of first five terms =3+7+11+15+19=55

Hence, the answer is 55.

Or  

We can use the formula for sum of A.P S  

n

​  

=  

2

n

​  

(2a+(n−1)d)

∴S  

5

​  

 =  

2

5

​  

×[2(3)+(5−1)(4)]=55

Answer 2

Answer:

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