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 Find a possible formula for the exponential function through the points (−2,100) and (1,4/5)

 Apr 11, 2019
 #1
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100 = ab^(-2)      ⇒ 100 =  a / b^2   (1)

.8 = ab^1    ⇒  .8 = ab   ⇒  .8/b  = a   (2)

 

Sub (2) into (1)  for a

 

100 =  .8 / b^3

 

b^3 =  .8/100

 

b^3 = (8/10)(1/100)

 

b^3  = 8/1000

 

b =  2 /10  =  .2

 

And

 

.8/.2 = a  = 4

 

So....the function is

 

y = 4(.2)^x

 

 

cool cool cool

 Apr 11, 2019
 #2
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thanks for clearing up some confusion 

Guest Apr 11, 2019

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