Question

find the 12th term of an AP if the first term is -12, last term is 20, and the sum of all terms is 80

Answer 1

Answer:

a=-12

an=20

sn=80

sn=n/2(a+an)

80×2=n(-12+20)

160=n(8)

n=20

an=a+(n-1)d

20=-12+(20-1)d

32/19=d

a12=-12+11×32/19

by solving we get

=6.52