Answer:
k=-8
Step-by-step explanation:
Isolate the variable by dividing each side by factors that don't contain the variable.
Amount decrease = 380 - 225 = 155
percent = 115/380 * 100 = 40.8 %
Standard form of an exponential function is y=ab^x
when x=0, y=3, 3=ab^0, so you can figure out that a=3
when x=-1, y=6, 6=3b^(-1), b^(-1)=2, b=1/2
so the equation is y=3(1/2)^x
