Answers

2016-06-22T18:48:06+08:00
1. 
 a_{9} =  a_{1}  + 9(d)
 a_{9} = x+ 9(3x)
 a_{9} = x + 27x
 a_{9} = 28x

2.

3.
 a_{45} = 5 + (45-1)(4)
 a_{45} = 181
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