Verified answer

Hi,

an = a1 + d(n - 1)

27 = a1 - 4(9 - 1)

27 = a1 -4(8)

27 = a1 - 32

a1 = 59

Sn = n/2(a1 + an)

Sn = 9/2(59 + 27)

Sn = 9/2(86)

Sn = 9(43)

Sn = 387 <==ANSWER

I hope that helps!! :-)

an = a1 + (n-1) d

so 27 = a1 + (9-1) (-4)

or a1 = 27 +32 =59

so Sn = n/2 { a1 + an}

= 9/2[ 59 + 27]

= 9/2 *86

Sn =387 ans

1/2(a+l) = Sn

an=27

a=3

9th term is the last term and that is a+8d

1/2(3-29)

1/2*-26 = -13