Question

Find an equation for the nth term of the arithmetic sequence.

a15 = -53, a16 = -5

A) an = -725 - 48(n - 1)
B) an = -725 + 48(n + 1)
C) an = -725 + 48(n - 1)
D) an = -725 - 48(n + 1)

Answer 1

an=a1+d(n-1)

every term increases by d amount

so
`a_n+d=a_(n+1)`
therefor

`a_(15)+d=a_(15+1)=a_(16)`

-53+d=-5
add 53 both sides
d=48

alright
an=a1+d(n-1)
an=a1+48(n-1)
use a15=-53
a15=-53=a1+48(15-1)
-53=a1+48(14)
-53=a1+672
minus 672 both sides
-725=a1

the equation is
an=-725+48(n-1)
answer is C