Question

An exponential function f(x)

Answer 1

Given:

An exponential function $f(x)=ab^x$ passes through the points (0, 12000) and (2, 3000).

To find:

The values of a and b.

Solution:

We have,

$f(x)=ab^x$      ...(i)

It passes through the point (0,12000). Putting x=0 and f(x)=12000 in (i), we get

$12000=ab^0$

$12000=a(1)$

$12000=a$

Given function passes through the point (2,3000). Putting x=2, a=12000 and f(x)=3000 in (i), we get

$3000=12000b^2$

$\dfrac{3000}{12000}=b^2$

$\dfrac{1}{4}=b^2$

Taking square root on both sides.

$\pm \dfrac{1}{2}=b$

For an exponential function b cannot be negative. So, $b=\dfrac{1}{2}$.

Therefore, the value of a is 12000 and the value of b is $\dfrac{1}{2}$.