Question

Find the sum of 12 terms of an AP whose nth term is given by aₙ = 4 – 3n make it for brainlist. only right answer. if not no brainlist............

Answer 1

Step-by-step explanation:

an=4-3n

if n =1

a1=4-3×1

a1=4-3

a1=1

if n=2

a2=4-3×2

a2=4-6

a2=-2

common difference (d)=a2-a1

d= -2-1

d=-2-1

d=-3

sum of 12 terms

n=12

sn=n/2(2a+(n-1)d

$sn = \frac{n}{2} (2a + (n - 1)d)$

s12 = 12/2 ( 2×1 + (12-1) × -3

= 6(2+(11)×-3

6(2-33)

6×(-31)

=-186