An equation whose variables are polar coordinates is called a polar equation. These equation are characterized by an r as a function an angle. Polar equations can be written in rectangular coordinates by certain relationships. An example of a polar equation would be r = 2sin∅.
There are (15 - 6) terms in between, therefore 9 terms in between. -8 to -62 ... there is a difference of 54 54 ÷ 9 = 6 Therefore it gets -6 each term. a6 = -8, a7= -14, a8 = -20 ......