Question

find the sum of the first 15 terms of an AP 2,7,12​

Answer 1

Answer:

an= a+ {n-1} ×d

Step-by-step explanation:

an =15

a= 2

d 12

15=2 +{n-1} ×12

15/2 = n-1 ×12

7.5 = n-1 ×12

now we are going to take n - 1 to LHS

N - 1 = 7.5×12

N -1 = 90

so

N = 90 + 1

N = 91

THE SUM OF FIRST 15 TERMS IS 91

Answer 2

Answer:

$\huge\mathfrak{Answer:}$

sum of an ap = n/2(2a+(n-1)×d)

using this formula the answer comes out to be 91

hope it helps u