tn = 1-4n
t12 = 1-4*12
t12 = 1-48
t12 = -47
tn =1/2 n+3/2
t12 = 1/2 (12) + 3/2
t12 = 12/2 + 3/2
t12 = 15/2
t12 = 7 1/2
9,4,-1
a1=9
d = 4-9 =-5
an =a1+d(n-1)
-146 = 9 + -5(n-1)
subtract 9 from each side
-155= -5(n-1)
divide by -5
31 = n-1
add 1 to each side
n=32
the 32nd term is -146