recursive rule

Rule:  a₁  =  16          a_n  =  ½·a_{n - 1}  

 

a₁  =  16  =  2⁴

a₂  =    8  =  2³

a₃  =    4  =  2²

a₄  =    2  =  2¹ 

 

Notice that each answer can be written as a power of 2.

Also notice that the subscript of the term when added to the exponent results in 5.

 

Combining these two ideas:  a_n  =  2^{5 - n}

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