For the following geometric sequence find the explicit formula.
{12, -6, 3, }

The formyla for a geometric sewuence is
An=a1×r^(n-1)
n standing for the location of the term
An standing for the term
And a1 standing for the first term in the sequence ( the 1 tells us it's the first term)
We need to solve for r since we are missing that constant
a1=12 (also a constant for the formula)
a2=-6
a3=3
Let's use a2 to solve for r
-6=12×r^(2-1)
-6=12r
÷12 both sides
r=-1/2 (the other constant we need to know
now write down the formula
An=12×-1/2^(n-1)