Express y as a function of x. The constant C is a positive number.

ln y = 9x + ln C

To express y as a function of x, we need to eliminate the natural logarithm (ln) on the left side of the equation.

Start by using the property of logarithms that states ln(a) + ln(b) = ln(a * b). We can apply this property to rewrite the equation as:

ln y = ln (Ce^9x)

Next, we can use the fact that ln(e^z) = z to simplify further:

ln y = 9x + ln C

Now, exponentiate both sides of the equation with the base e (which is the inverse function of ln), so we get:

e^(ln y) = e^(9x + ln C)

This simplifies to:

y = e^(9x) * e^(ln C)

Remember that e^(ln C) is equal to C since the exponential function e^x is the inverse function of ln(x).

Therefore, the expression for y as a function of x is:

y = Ce^(9x), where C is a positive constant.