-The arithmetic mean of number's a and b = a+b/2 -The geometric mean of number's a and b = square root of ab Note: A sequence is a list of numbers. An arithmetic sequence is a sequence that is generated by adding the same number each time. Arithmetic Sequence formula : tn=t1 + (n-1)d t1= first term n= term number d= difference  tn= ___ term A geometric Sequence is a sequence that is generated by multiplying the same number each time. (to divide, we use fractions) formula: tn=t1(r)^(n-1) t1= first term r= what is being multiplied n= term number tn= ___ term Example: 1.) Find the first four terms of the sequence and state whether the sequence is arithmetic, geometric, or neither. tn= 4n+12 n=1 4(1)+12=16 n=2 4(2)+12=20 n=3 4(3)+12=24 n=4 4(4)+12=28 It is arithmetic because you are adding 4 each time! Example: 2.) Find the first four terms of the sequence and state whether the sequence is arithmetic, geometric, or neither. tn=-2n+8 n=1 -2(1)+8=6 n=2 -2(2)+8=4 n=3 -2(3)+8=2 n=4 -2(4)+8=0 It is arithmetic because you are adding -2 each time!