# math

Given an exponential graph that are concave up and the points (1,4) and (-1, 16), give a possible formula of the function.

I plugged the variables into the f(x)=b times a^x and got:

4= b times a^1 and
16=b times a^-1

I am not sure where to go from here.

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1. huh? a^1 = 1 and a^-1 = 1/a, so

4 = ba
16 = b/a

now divide:
4/16 = ba/(b/a)
1/4 = a^2
a = 1/2
so, b=8

f(x) = 8*2^-x

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2. Thank you! I forgot that you could divide the two!

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