Question

The first and sixth term of an ap are -12 and 8 and the sum of n term is 120 the number of terms in

Answer 1

a=-12,a6=8

a+5d=8

5d=20

d=4

120=n/2(-24+(n-1)4)

240=4n(-6+n-1)

60=n(n-7)

n=60 or n-7=60

n=60 or n=67