Final answer:
The exponential function with a y-intercept of 9 and passing through the point P(2, 1) is f(x) = 9 * (1/3)^x.
Step-by-step explanation:
To find an exponential function of the form f(x) = ba^x that has a given y-intercept of 9 and passes through the point P(2, 1), we need to set up two equations based on the given information. When x=0, the function must equal 9 (the y-intercept), so we have:
1) f(0) = b * a^0 = b, which simplifies to b = 9.
Then, since the function must pass through point P(2, 1), we use this point to create a second equation:
2) f(2) = 9 * a^2 = 1.
Solving this equation for a, we get a^2 = \(\frac{1}{9}\), which means a = \(\frac{1}{3}\).
So, the exponential function is:
f(x) = 9 * (\(\frac{1}{3}\))^x.