C
Explanation: Rewrite 18 as 3^2 * 2
REASON: Factor 9 out of 18
Rewrite 9 as 3^2
Pull terms out from under the radical
Answer: 3√2
In mathematics: Arithmetic progression, sequence of numbers such that the difference of any two successive members of the sequence is a constant. Geometric progression, sequence of numbers such that the quotient of any two successive members of the sequence is a constant. so i chose b)Sequences