Review! :)

What is the formula for an arithmetic sequence?
****tn=t1+(n-1)d

Find the formula for the sequence 10,15,20,25,30,.....
You use the tn=t1+(n-1)d
Tn=10+(n-1)5
Tn=10+ 5n-5
****Tn=5n+5


how many positive two digit numbers are there that are multiples of three?
12,15,.....99
Plug it into your tn=t1+(n-1)d
99=12+(n-1)3
99=12+3n-3
99=9+3n
90=3n
****N=30

what is the geometric sum of the series formula?
***sn=t1(1-r^n)/1-r


Find the slope of the parallel line to: 4x-y=6.
Plug it into -a/b.
-4/-1
****4

Find the slope of the perpendicular line to:3x+2y=4.
-a/b
-3/2
***2/3