



 
Hi Rita, The subscript on the letter a tells you which term it is so
When we want to write an expression that is valid for a group of terms we often use a letter for the subscript and then describe the values that the letter can take. So for example you might say a_{n} = 3n for n = 1, 2, 3 or 4 rather than write a_{1} = 3, a_{2} = 6, a_{3} = 9 and a_{4} = 12. In your first example you correctly say that a_{1} = 9 and you also correctly say that 2 is multiplied by each term before to find the term that follows. Thus
So how do you write a general expression for all the terms beyond the first? To use mathematical notation in place of your phrase 2 is multiplied by each term before to find the term that follows I would say that
So here is my answer
You try the second example and write back if you need further assistance. Penny  


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