174k views
2 votes
Find the equation of an exponential function, f(x) = ab^x, given the following points: (3, 10) and (4, 30)

User Ggrelet
by
8.4k points

1 Answer

5 votes

Starting with the first point, (3, 10), we have:

10 = ab^3

And for the second point, (4, 30), we have:

30 = ab^4

We can now use these equations to solve for a and b. One way to do this is to divide the second equation by the first equation:

30/10 = (ab^4)/(ab^3)

Simplifying this expression gives:

3 = b

Substituting this value of b back into one of the original equations (say, the first one) gives:

10 = a(3^3) = 27a

Solving for a gives:

a = 10/27

Therefore, the equation of the exponential function is:

f(x) = (10/27)*(3^x)

Alternatively, we could have used the logarithmic form of the exponential function to solve for a and b:

f(x) = ab^x

log(f(x)) = log(a) + x*log(b)

Letting y = log(f(x)) and u = log(b), we can rewrite the equation in the form of a linear equation:

y = mx + b

where m = u and b = log(a). Then we can use the given points to solve for m and b using standard linear regression techniques. Once we have found m and b, we can substitute them back into the equation to get the final form of the exponential function.

User Iwein
by
7.7k points