Answers

2016-02-24T14:15:01+05:30
-15, -18, -21............

This is an Arithmetic progression
First term = a = -15 and the common difference = -18-(15) = -3

nth term of an AP = a + (n-1)d
    
                             = -15 + (n-1)(-3)
 
                             = -15 -3n +3
 
                             = -12 - 3n



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2016-02-24T16:22:13+05:30
-24
these numbers go in 3 tables so
-3,-6,-9,-12(-15,-18,-21,-24)
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